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Our aftercoolers may be good, but really? Salt and zinc cut the efficiency down to a quarter.
Under pressure you can see that two or three of the tubes have been compromised by corrosion
The buildup of corrosion internally put undue stress on the housing, throw in engine vibration for this result.
Again, corrosion between brass and aluminum are not all they’re cracked up to be.
Simple leakage of water past the aftercooler seal.
Where did my paper hand towel go t-
you should know the answer by now.
Peeled away we can see that the towel had been there for some time.
Zinc and corrosion gum up the aftercooler.
Again the expansion of corrosion crack a housing, less drastically in this case.
Corrosion from unchecked use.
On the left is the normal state of the housing, the right shows the effect of corrosion.
Looking for your impeller?
Oil mist and condensation form over time to add yuck and guck your once pretty aftercooler
These bent tubes show the result of an improperly installed zinc bouncing about the underside of the aftercooler.
More yuck and guck and oil mist turn into baby poop on your aftercooler.
A more advanced stage of corrosion, especially on the aluminum finned aftercoolers.
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Corrosion and salt across the fins reduces the area contacting air, thus re
Tony Athens | February 3rd, 2011
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I have been fortunate enough to have had the opportunity to build HYDRAULIC DRIVES for two sailboats in the last 10 years and both were quite fun projects. One was an 18 HP system on a small sailboat (Yanmar 2GM for power), and the other was a Yanmar 4JH3 100 HP twin drive system in the N.Y. 40 "ROWDY" which has been winning World Class races ever since (unfortunately, I don't think it's related to the repower). |
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The driving force for us going hydraulic was engine placement and adaptability to vessels that were designed for no motor in mind. Both systems worked beautifully and exactly as planned. We kept it very simple as to overall hydraulic design and worked around proven basic designs to keep efficiency loses to a minimum using an open loop system and non-variable displacement, or load sensing, pumps- (we went with large diameter hoses, valves and fittings, pumps and motor and fixed props matched for peak efficiency and used the engine RPM to control flow instead of bypassing fluid when cruising, and had a choice of engine RPM's at all other speeds. Much more efficient that way. Systems were super smooth, you could 'shift' at any RPM, and very quiet. Many people do not realize how much noise can come from a hydraulic system when designed in typical fashions with normally sized matched valves, hoses and lots of 90 degree fitting, and then having 2000-3000+ PSI fluid running thru them. |
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Yanmar 2GM - about 18 Hp at 3600 RPM the engine delivered all the power we needed at less than 2400 RPM for this "little sailboat" |
Isolated motor with separate thrust block -
note custom oil fed water seal |
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Small hydraulic pump using a "Lovejoy" drive coupling |
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As to overall efficiency, do not kid yourself. In the best case scenarios, working with closed loop systems operating at peak efficiencies and pressures, you may see 80-82% at best, but 50-70% overall would be the norm. So if you go hydraulics, don't do it because you think you are going to have a more efficient way as to transmitting power from an engine to the prop, you won't. Do it for other reasons. A properly installed conventional engine & transmission, and a PROP (as large a practical and a shallow shaft angle in relation to the vessel's LWL) matched to the engine and BOAT will be heads above as to overall efficiency for moving your vessel 100's of miles (cruising) under power. BTW, it's very easy, if you plan, to have a smaller & more efficient load sensing or fixed displacement pump driven off the engine used to drive auxiliary needs such as a dive compressor or generator for various electrical needs if hydraulics needs to be part of the power scheme. |
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Yanmar 4JH3 100HP at 3800 RPM -
never needed close to that much power to get hull speed |
Twin Hydraulic Motor layout -
Note 100% full isolation of the motors using Lord CB isolators similar to what AquaDrive uses on their thrust blocks |
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Valve and control - Simple lever system using Morse type cables |
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Hydraulic hoses were large diameter and were plumbed to use a minimum of hard 90's - All smooth bends to keep pressure drop to a minimum & fluid velocity down which all adds up to less noise and added efficiency. |
An interesting side note on the Rowdy. Going in, we always assume about a 40+% loss with a relatively low pressure hyd system (2500 PSI max WP - 20 HP in = 13 HP out), but it showed to be much less when looking at the prop we could swing and the performance of the vessel. Many advantages and many disadvantages but, in some cases, it is a good or "best" alternative, as it was in both of these vessels. Without extensive "hands-on" background in power train design and hydraulic work, stay away, as it is vastly more complex that it looks.
Tony Athens / Seaboard Marine Nov 2010
P.S. I forgot to add one bit of info for the "dreamers" out there. Although I said that the efficiency losses in these two hydraulic drive systems seemed to be less than expected and worked great, don't forget that these drives are being used for auxiliary purposes (maneuvering and /or relatively short term durations) and NOT for cruising 24/7. Even if they were only 25-40% less efficient than a normal gear/drive train set-up, that is a HUGE number when talking about traveling for days on end. |
Tony Athens | November 15th, 2010
Understanding Low Power Troubleshooting
How engine loading and propellers interact with vessel performance
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When troubleshooting a LOW POWER symptom, or a low RPM issue on any high performance marine diesel that uses mechanical fuel injection (meaning NO Electronics, or a true diesel that can run WITHOUT electricity), this is how we go about it (applies in 99 % of the low power / low RPM issues that I have seen). Although much of the same principles apply to the most modern electronic engines, because of the very sophisticated electronic control of the engines' fuel system, sometimes you need more than a visual of the exhaust output to guide you and get you started in the right direction.
Hopefully, these few paragraphs may save you going thru an expensive and time consuming learning curve, rather than following many of the old wives' tales & typical "dock talk" floating around in this industry that typically always leads you down the wrong road and becomes very costly without even finding the problem.
This is where we start (a VISUAL of the exhaust leaving the vessel, under your normal operating conditions): |
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If you are seeing any dark or black smoke during some or all of the operational RPM range, you most likely ARE NOT experiencing a fuel restriction problem. I am going to stress that again. |
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This IS NOT a fuel supply or restriction issue (clogged fuel filters). You are either overloaded during some or all of the engine operational range, or you are not getting enough air (this can be from one or multiple reasons). Also understand that on many planing hulls, during the acceleration mode from 9-15K or so (getting over the "HUMP"), some, to more than "some", black smoke could be perfectly normal as the engine pulls close to its maximum torque during the 10-60+ seconds it may take to get the vessel up on top. This would be dependent on the vessels planing characteristics vs its weight and the HP available. |
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If you are not getting RPM (of course you've already verified that your tachometer accurate, is right?), or the past speeds you used to have, and you have NO dark/black smoke, then, you are not getting enough fuel your throttle linkage is not making full mechanical throttle, or your fuel solenoid linkage is not reaching the full mechanical stop or settings. These 3 items cover most all complaints when you DO NOT have dark or black smoke to break this down to the next level: |
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Low power / Low RPM and you have DARK smoke:
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Propping issues: You are OVER PROPPED (overloaded or under powered in the vessel's current configuration - call it what you like). Regardless of why, being overloaded is directly related to the propeller matching the vessels current running configuration, weight, vessel bottom condition, windage, or running gear issues/conditions, but all of these go back to the prop as they all make the engine work harder because of these conditions, and slow the vessel down overloading the engine. Also, remember the term "external to the engine" as you read further. |
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AIR issues: Not getting enough air can be caused by a dirty/collapsed air cleaner, a leaking turbo hose, a filthy aftercooler or air restriction inside the aftercooler, a worn out or partially stuck turbo, or a poorly ventilated engine room. Any combo of these can restrict air to the engine causing dark smoke and further, low power. |
Maybe it's just one of your engines (like it's trying to carry all of the load or won't catch up with the other one ?? It doesn't matter, if you have dark smoke, it's because of one or both of the above.
Low power / Low RPM and NO DARK smoke:
If you have low power or are not getting your RPM, AND you are 100% sure the exhaust color is NOT DARK, then most likely you are not getting enough fuel - this can be from clogged fuel filters, clogged fuel lines and pick-ups, suction air leaks in the fuel supply, out of adjustment throttle linkage, the run solenoid not pulling up the fuel lever all the way, a broken return check valve causing low fuel pressure, bad fuel lift pump, lazy injection pump aneroid, and maybe a few others. All of these can contribute to not getting enough fuel and all are relatively easy to troubleshoot and correct.
Some Easy Checks & Solutions to not getting enough fuel (remember you have NO dark smoke): |
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Checking the throttle or fuel solenoid control linkage (a more common issue than you'd think) itself is super easy to figure out. Adjust or check the linkage or control mechanism until the lever or shaft hits the stop and/or goes slightly into the spring override ( if the injection pump is of that style). This can all be done with the engines turned off, at the dock. |
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Clogged filters are easy to change and if you have a vacuum gauge installed you will "see" the issue. |
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Checking for a bad lift pump or return line check valve usually requires a pressure gauge to be installed some place AFTER the on-engine lift pump. |
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Until you do all of the above, no sense in getting into more complex things like pick-up tube issues or aneroids as 99% of the time, you have already fixed the issue by doing all the above. |
Basic cost effective steps in low power troubleshooting
and where to go next
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NOW, ask yourself...
Have you performed the most basic steps of "Low Power" troubleshooting listed above? That's NUMBER ONE and until you have ID'd what your true symptoms are that match the above steps, you do not need to go farther. Remember, it starts with a visual of the exhaust color and then it's either YES or NO as to dark or black smoke.
No Help & still at a loss & want more?
Let's go back a tad to where you thought things were OK.. Do you have any good data from the past as to your performance "then"?.. This is the type of info you'd need to move forward in a "logical" manner - (example follows of operational data for your vessel): |
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Six months ago (or whenever) your vessel made 28-29K's at 3600 to 3650 RPM (at or close to the manufacturer's rated rpm) loaded as you typically use the vessel. |
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You cruised at 2800-3200 RPM and all was good-You were a happy camper. Your cruise speeds at those RPM's were as follows:
2800 RPM = 18K's
3000 RPM = 20K's
3200 - 3300 RPM = 22-24K’s (the vessel really started to "come alive"
Plus, when getting "over the hump" the boat was spunkier and seemed to do it with a minimum of struggling and a minimum of dark smoke. |
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Now, just all of a sudden you leave the dock a month, two, or three later for a typical trip and the engine seems to have lost its vigor and after getting up to your typical cruise RPM, you seem to be traveling slower. You check things out & push the throttles up to the stops, but you don't make the same RPM (or speed as before). You are now down to a WOT RPM of 3400 on one engine and 3350 on the other, & WOT speed is only 23-24 K's. Plus, to make matters worse, at your cruise RPM of 3200, the boat is only making 19.5 - 20K's. What's wrong?? Playing with the trim tabs doesn't help, and next you go for the fuel filters (very typical). Got to be the problem?? No Help !! Anyway, you finish the trip and over the next week or so you start asking around. |
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Does the above kinda fit where we are at this point? If so, you need to read what comes next (maybe a few times) and let it SINK IN. This is where understanding how engines, boats and propellers work in unison, and all together affect how fast the boat travels. What follows is what I feel is the most important principle of how boats, engines and propellers interact and the single most misunderstood principle in the industry as to vessel performance. And, that even applies to those who are supposed to understand engine and vessel operation - Maybe your "seasoned" mechanic or friendly surveyor qualifies ??? |
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The first thing to understand is that your vessel's propellers move the boat. All the engines are doing is turning them. Spin your props at "X" RPM and the vessel travels at "X" RPM or speed. It's that simple... Think about it and then think some more, so the most basic of vessel operation has sunk into your head. |
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Now we have to go back again and look at what was happening 6 months ago. Your engine made 3600 RPM and your PROPS were rotating at 1800 RPM (you have a 2:1 gear ratio) making the vessel travel at 28-29K's, and at 3200 engine speed rpm (1600 prop RPM) your vessel made 22-23K's. Correct? Again, remember it's the props that make the boat move forward, the engine is only turning them. |
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Now it's today and we have the same engine and we are at the 3200 RPM with the same props turning at the same 1600 RPM, but the boat is only traveling at 19-20K's.. Hmmmmmm ??? |
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Let's think long and hard about what is really going on. The props move the boat !! The engines are just turning them at the same RPM. But the vessel is going slower at this SAME RPM. |
THINK and THINK some more!!
The Answer: It's not a fuel supply issue (clogged filters, air leaks, etc, etc). It's not injectors. It's not the turbo. In fact, to put it bluntly, IT'S NOT an engine related problem. It's a BOAT ISSUE, or a problem that lies EXTERNAL to the engine. Remember a few paragraphs back I said to remember that term?
If this still does make 1 + 1= 2 to you, let's look at it this way. If the props are still turning the same RPM but the vessel is going slower, it's no different than the following example - Your are cruising along at 22'ks at 3250 RPM with your 100 gallon bait tank full of water and bait ' "loaded as you use the boat" - You start dumping the 800 lbs of water and over the next 4-5 minutes you stare down at your vessel speed and now you are averaging 23-24 K's, yet your RPM is still at 3250. If you had a boost gauge you would have seen your boost was higher before you dumped the water, yet after losing the 800 lbs you are traveling faster and your boost is down a pound or so. If you had pyrometers, they may be a tad lower temp than before. How could that be? Simple, the engine is working easier as you have REMOVED something external to it—WEIGHT in this case. Now start filling the bait tank and watch the opposite occur - Prop RPM the same, but the vessel slows down a knot or two, and the engine is now working harder again at that same RPM. The same thing applies to other things that affect engine performance and vessel speed at equal RPM's as before - Bottom condition, prop condition, windage, and of course, any type or amount of ADDED weight. And once any of these EXERNAL FORCES can get to a point to where you are past the maximum HP the engine can produce (at any RPM) , you are now in an OVERLOADED condition caused by something EXTERNAL to the engine - This is a VESSEL related issue, not an engine related issue and since we are trying to understand these external forces that affect the engines performance, a propeller is the main force that is external to the engine. |
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This water skier would be an example of a force EXTERNAL to the engine. Cut the rope and the RPM stays the same but the vessel picks up 2+ Knots |
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If you CAN'T buy into this, then my answer is also very simple. YOU ARE IN DENIAL, and lack the most basic understanding of how a vessel's performance interacts with the engine's capabilities. And if your mechanic is still picking away at your back pocket replacing injectors, rebuilding turbos, etc, then you are in "double denial" and your mechanic, surveyor, friend or ?? is a buffoon as all you had to do is understand what you just read "propellers move boats - engines only turn them".
Lets go thru some of these basics again and add some more to our database before we start replacing things like filters or worse, parts like injectors. |
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Strobed your engine and certified tachometer accuracy?. This should always be done and done when you first start using your boat, especially if performance was a key part of the reason you bought the boat. In so many words, an accurate tachometer reading, paired with the manufacturer's power curve data and ratings, is the starting point for ALL engine & vessel operation parameters. |
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Confirmed that the fuel stop or solenoid lever, and throttle linkage are 100% into their respective stops when at WOT? This basic mechanical check is overlooked quite often with $$ being spent unnecessarily more times than you really want to know about. |
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And, for the guys who want the very most they can get from their engine without going over the edge - Have you considered installing a boost gage (power) & pyrometer (safe cylinder temps) ? - this is the ONLY way to gauge horsepower & the engines safe operation output outside of having accurate instantaneous fuel consumption gauges. These gauges can be super important tools to allow you to have baseline engine performance data for now and for later when you start having issues. If maximum performance is part of your agenda, consider installing these gauges and learning what they are telling you as it's money & time well spent. |
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Installed BOTH fuel vacuum AND fuel pressure gauges, and recorded results at speeds in gear and out of gear above 1600-2000 RPM when you think you have a fuel supply issue? Most mechanical engines allow you to do this at the dock in neutral. Although a vacuum gauge is much easier to install, it does not always tell the whole story. If you can't make the needed fuel pressure after the engines lift pump, it won’t matter if the vacuum gauge is giving you a GREEN light (and many times they do). |
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Installed a clear line with a loop in it just before the engine in case you think you have an air leak?? |
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Measured exhaust back pressure? (This is a low number typically measured in inches of water column or MM of Hg (usually in the 1/2 PSI - 2 PSI range if you think "PSI"). Turbos can slow down with age and /or wear (excess pressure over time), and from saltwater getting to them because of a poorly designed wet exhaust system. All of these can cause dark or black smoke affecting the engines overall performance (lack of air), and all may happen over a period of weeks to months. If you had installed a pyro, most times you'll see this coming. |
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Peeked at return flow to insure it generally matches the spec sheet as to total fuel flow??. Most mechanical engines in neutral and at higher RPM's will show close to 90% of maximum fuel flow going into the return line. |
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Checked injection pump timing?. Not a likely issue unless someone has R&R-ed the pump, but something that can be a prudent thing to do after all of the above have been performed. |
NOW, to move on, a trial run or mini-seatrial is important to "see" how the vessel runs AFTER these simple steps are gone through so many times the vessel operator does not really "see" what is really happening but only knows the power is low in comparison to some earlier time in the vessel operation.
When an engine has low power complaint issues or symptoms, and these steps are by-passed (expensive mechanical parts are changed/rebuilt before these most basic operating parameters are checked) it's far from the smart way or cost effective way to go about finding the problem. The order in which I listed them would be close to how I would go about finding the issue, unless I saw something on a sea trial that appeared likely to be the problem. This is where a truly experienced and passionate mechanic can really make a difference, and IMO, you will rarely find one of these that does not work for himself. In so many words, a "factory certified" mechanic doesn't hold much water in my book if he is still working for a major engine distributor as all they seem to think is to be sure they get the needed "billable hours" when they return to the shop. Solving the "reason" to the issue is usually not part of their plan. But replacing parts is always part, regardless of "WHY". |
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Back to our "mini-sea trial": The two most important operational parameters that I would look at (a visual look based upon 25+ years of looking at 1000's of engines) on the first run: |
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How much crankcase by-pass you have at 1000 RPM in neutral vs at 2000 RPM+ in gear so I could get a feel for the general condition of the engine, AND.... |
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Confirming the color of the exhaust smoke during any type of "performance lagging" condition….... |
Hopefully all of the above will help you diagnose the issue quicker and cheaper. REMEMBER, that in just about every case if you have any dark smoke, it's not a fuel restriction issue or under fueled condition.
As to injector issues which always seems to come up with inexperienced mechanics or ones looking to make a quick & easy buck, that's just about never the issue unless you know water went thru the system. And then, it's just about always, tons of WHITE smoke.
If we were to talk about a specific and very popular engine, the Cummins 370 Diamond, IMO, AN ACCURATE 3100 RPM loaded for bear is the minimum you should see, but we prefer 3125-3150. And, BTW, this same 100++ RPM over-rated RPM is a must for any engine in this class (50-60+++ hp per liter). Remember, as the HP per liter climbs, then being able to reach over the minimum rated RPM becomes even more important IF you want decent engine life and want maximum performance out of your engine. |
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If you have a later electronic engine with accurate fuel and % of load data, then instead of using my rule of 100++ over rated, you have to compare the total fuel consumption at the engines RATED RPM (print out the manufacturer's performance curve) vs what you have on your digital gauges. If your HP per liter at rated RPM and load is above 60 HP, IMO you never want to be propped to have the engine burn more than 95% of its max fuel burn at its exact rated RPM. Load % should also be at 95% or less at rated RPM but may show 100% at WOT as your engine will exceed that rated RPM by 30-60 or so depending on the electronics and programming of the engine. A touch more tricky to understand in some ways, but because of "digital gauges" with a little understanding and homework, you can prop your vessel for maximum performance while also being sure you are not going over the edge on these very high performance marine diesels.
Tony Athens / Seaboard Marine
Aug 2010 |
Admin | October 7th, 2010
Mr. "6BTA 5.9" Cummins owner,
Welcome to the world of "couch engineering". Both teams of engineers who designed the Cummins factory-supplied seawater pump (Sherwood 17xx), and the ones who designed the way it is installed on this engine, cramped behind the engine mounting bracket, IMO, need to be hung by their cahonies. I'd gladly be the lynch man as this whole mess has caused way too much grief over the past 15 years or so.
Here are some suggestions that may help the next time around when it's time to deal with your seawater pump. You do have some long term solutions, but it's up to you whether spending some extra effort now will be worth it over the next 5-10 years that you may own your boat...
Access is the biggest problem for the 6BTA's - It's the maze of plumbing around it, coupled with the poorly designed engine bracket, that makes it close to impossible to service or replace without drawing blood..... |
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The 330-370 Diamond "MAZE of Plumbing" and Sherwood seawater pump |
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SOLUTION - Remove or loosen the top nut on the isolator in that corner, completely if you like - the engine should not move as gravity will keep the engine in place. Now you have to figure out a way to jack up that corner of the engine ever so slightly (maybe 1/16"-1/8" inch) to where the washer under the bracket is loose. This tells you the weight is off the isolator. From there, again depending on access, either remove the two bolts holding down the isolator to the boat (stringer / bracket or ?) and / or the 3 bolts holding the engine bracket to the engine and remove the items by wiggling them away until they are out of the way. For sure this will be a frustrating job. Now you can remove the two 12 mm dia bolts holding the pump to the engine and slide out the pump. You DO NOT have to touch the 4 smaller bolts holding the pump to the large Diamond shaped plate as all that does is loosen the pump on the face plate. But if you were to remove them, it does allow the pump to "wiggle" more - some say it makes the process less painful ?? |
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Now before you reinstall your repaired pump or a new one, ask yourself what you could do NOW in order to make the NEXT TIME you need to service your pump a lot easier.
You do have some logical choices at this time that make some real sense.
1) Look over the isolator and the vessel mounting arrangement to see if you could add a 1/2 inch spacer behind the mounting bracket. On many boats this is easy, on others it is not. You need clearance on the outside of the isolator base to slide it out 1/2 inch. But if you can, then this ONE modification makes a world of difference. Look at the pictures. Use 3 new 12MM high strength bolts (8.8 or better) about 10-15 MM longer than the stock ones and when re-assembling, tighten to about 80 ft-lbs. Use lube on all bolts.
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2) Consider removing the maze of plumbing and other things that you, more than likely, DO NOT NEED.
Remove the fuel cooler & related plumbing (if you have it) permanently as in 99% of the installs this is not needed, remove the fuel/oil manifold block as it does absolutely nothing functionally other than cause clearance issues and then you'll be able to service your seawater pump down the road much more easily. |
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Partial modification: Stock Sherwood Pump using a "Wire Hose" to connect to the aftercooler,
and showing the "fuel block" removed with the oil pressure sender remounted. |
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3) Lastly, consider using a better pump that will actually clear the front mount without any bracket modification. This will really clean up your 6BTA to make the engine so much simpler, IMO, safer to use and maintain, as now you can actually deal with it at sea when rockin’ & rollin’, if adrift… |
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Simplified 330-370 Cummins Diamond shown direct fuel hook-ups for supply & return |
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RUKO Impeller puller - Around $200 for the "kit" |
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Some other help: Proven tricks on IMPELLER removal and installation that may help - To remove the impeller, this works best if you must leave the pump attached to the engine, or even do it on the bench. Remove the back plate, spray inside/all around the impeller and shaft area with WD-40 - Bump the starter so the engine revolves (if on the bench, spin the pump shaft a 1/2 turn both directions). Do it again / twice to three times. This breaks the rubber bond in-between the impeller and the pump housing. Then start pulling on the impeller with pliers, or use a "Ruko" puller (they are the best, although expensive).
You may have to spray and rotate more as it comes out. When installing a new impeller, also use plenty of LUBE (grease, hand lotion, soap, Vaseline, etc.) on all parts and inside the housing when installing. You CANNOT use too much. And, DO NOT WORRY about which direction you twist, rotate or push - the impeller vanes DO NOT care how they end up - Another "old wives' tale" that will not go away. |
Servicing the pump if you are not replacing it - If your seawater pump has been in salt water for a few years, I do not recommend just replacing the impeller without replacing the cam and inner wear plate. Both of those particular Sherwood parts corrode excessively over time (Marine Age seems to make them dissolve away even without high annual hour use), and the corroded / worn parts can quickly eat a new impeller if not replaced.
As to the drive "key" that is supposed to be easy to deal with, and also be square in shape, if you are having issues sliding in the impeller with the "key" in place, you need to be absolutely sure why your impeller will not go in. If the key is wedged or ??, and the impeller is sticking out a tad, putting on the back plate and tightening it flush is a NO-NO, and could cause some very serious damage. Most likely, the instant you bump the starter, the pump shaft will shear off at the gear and the drive gear is now loose, spinning inside the timing case - a major disaster is just seconds away. Too bad Sherwood forgot that a splined shaft is so much easier to deal with.
Hopefully the pictures here will help guide you and help anyone trying to service or replace this pump. Even better, do some or all of these suggestions by up-fitting your Cummins "B" BEFORE you install it in your boat if doing a repower. You'll pat yourself on the back for years to come...
Tony |
Tony Athens | March 4th, 2010
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 Download Envirovent Flyer
For the past 15 years I've been thinking about (and trying to understand) the crankcase breathing system on the Cummins B Series engine in typical marine applications. I wanted to develop a simple and cost effective CCV system for this much desired engine. This period of "contemplation" goes back years ago and sprang to life during a plane ride with my Cummins distributor/sales rep, Mike Hoffman. It was the only time I ever flew in "First Class" and after a few bottles of red wine, we coined a name: "ENVIROVENT." Now I feel that I have something to offer; a simple and effective CCV system that will make most everyone happy. But first I'd like to give some history and some basics for understanding the crankcase venting system that is used on this particular engine, along with the ABC's of what a CCV (CLOSED CRANKCASE VENTILATION) system is supposed to accomplish.
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Since first introduced to marine service in 1985, the Cummins 5.9 liter "B Series" has become the most popular, well respected, and most sought after marine diesel in this size range ever produced, and this status is well deserved. Around late 1988 or early 1989, the engineers at Cummins released the 6BTA 300 B version (CL 970) and along with this new high performance rating, they also introduced a low profile, flat cast aluminum oil pan. Somehow, during the design of the new oil pan, the design team assigned to this new oil pan project missed a very important engineering design feature that should be part of any oil pan design... The pan was so shallow (about 9" lower than the center of the crankshaft), that under normal operating conditions the connecting rods would "dip" the oil. Not good and goes against all of the published literature I have ever read INCLUDING Cummins' own oil pan design requirements. As time passed, and the RPM range of the B grew (3000+ with the 1997 release of the 370 Diamond) the rod "dipping" now became more like rod oil whipping. Instead of deepening the pan an inch or two, the engineers designed a new baffle system to help contain / control oil sloshing in the oil pan... Strictly a band-aid approach IMO, although it did help some. I think the most prevalent application part of the overall design approach Cummins chose was that the engineers DID NOT understand typical marine vessel operation (planing vessels for sure) in that under normal operation, the nose of the engine rises substantially and the oil in the shallow flat pan flows to the back of the pan and rises causing even more turbulence and oil whipping leading to higher than normal crankcase vent pressure. |
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Basic flow chart of any CCV System - Racor CCV shown only as an example of how a CCV flows crankcase by-pass to the engines turbocharger or air intake. |
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Now comes the other part of the equation and that is, how to control this excessive oil whipping and to mitigate the typical issues (aerated oil, extra heat, pressure and possibly even a HP loss) that accompanies this. The standard location of the crankcase vent is the left REAR side of the engine (side tappet cover) and/or behind the aftercooler (SWAC 6BTA's). This was a fine location for the Dodge trucks and all the industrial applications (they had 12+" deep oil pans), but for the typical marine application, this particular placement of the vent exaggerated an already touchy issue. With the oil backed up against the rear of the oil pan, with the connecting rods whipping the oil, with continuous higher RPM's than you would see in non-marine applications, with the flat shallow oil pan coupled with a nose/front up attitude (2-15+ degrees) of the engine during normal typical operation, what you ended up with was oil being pushed out of the breather in varying amounts. Sometimes a few drops over a course of a day's fishing, and sometimes enough to lead an operator to think he had problems with the engine as "blow-by" at times would seem excessive. What also would happen with this shallow pan, was that oil level was hard to measure accurately because there was only about 1/2" between the amount for low (13 QT mark on the dip stick) and high (15 qts). Between this difficult-to-measure amount of oil in the pan and the natural tendency of an operator to keep the oil at the high mark (or think that "more" has got to be better than less when it comes to oil) all worked together to further exaggerate the problem of oil mist being pushed unnecessarily out of the crankcase breather or "draft" tube, as it is called in automobiles.
Over the ensuing years between 1997 and 2004, the engineers at Cummins tried many different methods to help contain the oil in the engine. First were baffling changes and new dipstick designs for the pan itself, and next they followed with new engines being shipped with a small plastic bottle attached to the breather tube (short lived). After that, we received engines with the rear side vent attached to a new front timing cover breather that had a "T" and a draft tube going down and tucked behind the injection pump and seawater pump. This was probably their best effort, although the installation or maintenance of this design was impossible to deal with as one could not realistically reach the tightly tucked-in hoses or clamps making up the device. Along with this, they also changed the orientation of the side cover tube from pointing DOWN to UP... Basically I lost track of the different methods and parts used to accomplish such a seemingly simple task - Having a simple crankcase ventilation system.
This is what we have learned thru all of this over the years.
For all inline or conventional drivetrains with the engine facing the bow of the vessel, the Cummins B series engines like to breathe from the front timing cover. Reason?--It is because it's a very "calm place" inside the engine and the timing case, due to its base design, has a tendency to condense much of the oil vapor and return it to the pan (due to that slight cooling effect and large surface area of the steel cover). With this knowledge we went about designing a simple and effective way to allow the engine to breathe from this area. We adapted some already made Cummins' parts to allow the installation of a special S&B crankcase type air filter (known as a PCV vent filter in the automobile industry). Our first and still used design was really simple. We capped off the rear side vent tube, installed this front timing case vent and now had a super simple solution to the problem of a "dripping vent tube". Too simple but very effective. As an added plus for this system, simple oil filling from this location is now easy when overhead clearance is minimum. |
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Simplest of all - Cummins "B Series" front crankcase vent developed by Seaboard Marine |
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But like any crankcase engine vent, even the slightest amount of crankcase fumes that are released can be objectionable in many installations. Cummins knew this too, and along with the market's demands for having a super clean and decent smelling engine room, Cummins started offering the well proven and highly regarded Walker AirSep as an option for the "DIAMOND" Series of mid-range engines (B and C series) that were released around 1997. I believe Walker Airsep ( an air cleaner and oil/fume separator in one) was the first CCV system used in marine service that was widely accepted and proved to be a godsend to 100's of Detroit 2-stroke owners where the Airsep proved its worth in reducing oil leaks and oil mist in small "boat type" engine rooms. Other companies also saw a demand for a "closed type" crankcase ventilation system - and before long, the "CCV", as they are known, were made in different designs and being marketed by companies such as Racor. Along with the market demands for a CCV product, the EPA was closing in with new emission standards that would effectively require a CCV system on all internal combustion engines. The push was on !! |
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Walker Airsep Installation on a Cummins 6BTA Note: Owner had re-routed hoses from engine vent to the Airsep to help mitigate the oil accumulation issues with the original factory installation. |
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As to understanding what a CCV (Closed Crankcase Ventilation) is and how it works is quite simple. In its simplest of forms, a CCV system is merely a mechanism that enables the normal crankcase fumes to vent thru a hose to a "low pressure area" (a tube from the engine's air intake-the "low pressure area") and allow the "fumes" to be burned during combustion, while separating most of the liquids. In actuality, I am not sure why this is called "closed" (IMO, it's not really closed in the normal sense, like a closed "bottle" or refrigerator), but it makes the venting "out of sight and out of mind", so that must be the definition of "closed" in this case. Yanmar and some others use a very basic system by putting the crankcase breather hose near the air inlet and accomplish this "low pressure" thing, although this does not meet the meaning of a "closed system", but can act in a similar fashion under some conditions.
Although the Walker system worked extremely well for 2-Stroke Detroit owners and possibly other makes of engines, this was not always the case when installed on a Cummins "B" series engine. The base design of the "B" and its own inherent crankcase venting problems have a few conflicting issues that prevents the Walker system from performing as intended in many instances. This really is not because of a problem with the design of the Airsep (it's quite clever and works well in many applications) but rather, the way it must be installed on the Cummins B.
By design, the accumulated or condensed liquids in the Walker Airsep drain out the bottom of the installed unit thru a tube connected to the engine oil pan (because of a drain tube check valve.) This valve should ONLY open when the engine is not running - (normal crankcase pressure during operation keeps it closed). Well, again we have overlooked a flaw in the system in that these liquids, in many cases, are asked to drain thru this drain tube that can be level, or even "uphill" in many installations. Since "gravity" is needed for draining to occur (along with a working one-way check valve that is supposed to open from the WEIGHT of the liquid accumulation above it), one can see that this might not occur in many installations or under certain circumstances. The air inlet of the turbo is quite low and aft in relation to the oil pan of the "B" (that's where these liquids are supposed to drain). Couple that with any nose up attitude of the engine, and if one looks at a standard Airsep installation on the "B", it is easy to see why problems with draining these liquids could and do occur. The other base flaw and potentially more troublesome in the adaptation of the Airsep to the "B", is the routing of the gases AND liquids to the Airsep itself. In most all installations, the vent tube hose goes down first and then turns UP, forming an upside down loop or "sink trap." What happens in as many times as not, is that the drip by drip oil expulsion of the venting system on the "B" fills this sink trap to where the crankcase is now closed, and effectively, one of two things can happen depending upon the operation and condition of the engine when this occurs. The pressure from the crankcase coupled with the suction or low pressure area from the Airsep itself, slugs a bunch of liquid into the collection chamber of the Airsep-In simple terms, the system cannot deal with it and the liquids are now sucked thru the turbo. This leads to premature turbo fouling and worse, aftercooler fin contamination and clogging. A second result of this crankcase vent hose sink trap is that as the pressure builds to excessive levels, the gasket underneath the side tappet cover blows out resulting in quite a mess. Other issues that we have seen over the years w/ the "B" and the Walker Airsep adaptation, are stuck one-way drain valves. We have found them stuck in the open position causing oil to pump up into the Airsep and then into the engine, and also stuck closed leading to oil accumulation inside the Airsep and then being sucked into the engine. To eliminate this potential problem, we would suggest yearly (or more often) inspection, maintenance / replacement of this valve to insure proper operation. It's usually located at the bottom of the drain tube just before the connection of it to the oil pan.
This leads us to another issue that we believe is something to consider for any type of CCV system. The liquids that accumulate in any type of CCV are typically composed of oil mist, condensed water vapor, and condensed blow-by combustion chamber gases. The gases, along with water vapor, are parts of any engine's normal operation and contain small amounts of acids and other combustion by-products. As the engine wears w/either normal use, or thru lack of proper maintenance, installation issues and proper operation, these combustion by-products increase dramatically in amount and now are looked at as excessive "blow-by". We now have more of these "liquids" to deal with, and IMO, I would NEVER want to return this highly contaminated "liquid" to my engine. All one needs to do to understand why is to take a sample of it to your favorite oil analysis dealer and then wait for the results. |
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Another popular and well designed CCV unit is marketed by Racor. This unit is standard equipment on many new engines including the Cummins QSM some John Deere and Caterpillar models. Unlike the Walker Airsep system, the Racor CCV is a "stand alone" unit and needs to be connected to a separate air cleaner to have the "low pressure" needed to evacuate the gasses. The unit, as designed, separates liquids thru an internal filter and drains them back to the engine oil pan. We like this unit as it does a very good job as a CCV system, but in all installs, we remove the drain hose connected to the oil pan and collect them manually as needed, and then dispose of them. Simple modification and, in normal engine operation, this typically only needs to be done every 50 hours or so. As to long term high hour use, the unit does require a filter replacement (I believe Racor recommends every 100 hours) and periodic cleaning inside. Although not recommended by Racor, based upon our long term experience with the unit, we believe that it works better AND requires less maintenance when hooked up in REVERSE flow... Again, this is IMO, and is from years of field trials and experience and not in the laboratory or on the test bench. |
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QSM-11 with factory Racor CCV installation |
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Now that we know something about crankcase ventilation and CCV's, listed next are the favorable design characteristics of what we feel would be "perfect" CCV system.
In an ideal world, it would be nice to not let the engine ingest anything but the cleanest possible air. But, this is not the case nor will it ever be, at least in the marine environment. Marine engines must operate in the confines of a small engine room where just the engines need for combustion air at cruise speeds will typically cause an air change in the engine room 1-3 times per minute. Just figure it out - IF you are using 400 "cruise HP" (about 20 GPH) to move your vessel at 24K's, air consumption is about (or over) 800CFM.... Every diesel engine has varying degrees of "blow-by", and without some type of CCV, where do you think this blow-by ends up? All around your engine room (some condenses on the colder surfaces of the engine and engine room, but most of it goes into the air cleaners. The less ventilation you have, more will find its way back quickly to your air cleaners. In just about any engine room, when you look at the back of an alternator, you'll see signs of blow-by condensing on the back surfaces or on some of the internal heat-sinks. The fan on the alternator sucks in ambient engine room air, and most any vapors in your engine room will condense there. If you have nothing there, then you have an exceptionally clean running engine and great ventilation besides, or you have a good CCV that is working well. |
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A few features that make a good CCV system: |
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A good CCV will limit the amount of vacuum on the system and / or be adjustable for individual applications. This is an important design function of any CCV unit and can be accomplished in many fashions. We prefer a much simpler approach than most other manufacturers of CCV units.
Since our unit is "engine specific" as to sizing, the unit and connection assemblies limit the vacuum by design and actual size, and do not rely on an expensive "vacuum regulator" with springs and diaphragms that is far from "maintenance free". |
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A good CCV unit will not let liquid into the turbo or allow those ugly condensed liquids back into the engine, but will collect them as needed before they make it that far. In a nutshell, the perfect CCV would be one that could ingest all the normal (and a little extra) crankcase bypass from modern "state of the art" high speed marine diesels, separate all of the gases from the "pukey liquids" that will foul aftercoolers, turbos, etc., let the liquids be captured and drained in a convenient way to be discarded, and then burn just the captured gases / crankcase fumes, AND will not create some other high maintenance problem. |
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A good CCV system will make it easy to capture and drain those liquids. You don't want that nasty "puke" as I call it, back in the engines oil pan. |
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A good CCV system is simple to understand how it works. |
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A good and well designed CCV system is simple to install. |
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A good CCV system is simple to maintain AND inexpensive as to long term maintenance. |
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A good CCV system should have many years of field testing under the varying conditions of actual use and be designed for specific engines-I know for a fact that "one size", or type of installation, does not fit all !! |
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And lastly, a good CCV should be relatively inexpensive to upgrade from your existing "open breather". |
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Our new "Envirovent" system meets what we think are the features that make a good system, plus the system is designed specifically to the "B" series mechanical engines (Cummins 4BT thru the most popular 6BTA Diamonds). Although the general design principles we have used to develop the system and share with the general public could be applied to many other engines (we do on a limited basis), we are just a small company and only focus on the engines that we deal with on a day to day basis. As a reader of this article explaining our design ideas and "politics", we welcome you to glean our knowledge and expand on it to fit your own needs.
During our design phase, we had the S&B filter company put together a small PCV filter for us (you can call it our "vacuum break" limiter), and with that, our base design allowed a unique adjustable feature by tailoring the unit for engines with both normal and excessive crankcase pressure / blow-by. How? Via the way it is installed or clamped on the installation neck in relation to the "open" volume or area that is exposed to the low pressure caused by the connection to the engines air cleaner. No expensive "monkey motions" to fail or that need maintenance like diaphragm type vacuum regulators. The combination of the timing cover ventilation tube arrangement with this filter allows for a great low pressure adaptation, but "quiet spot" on the "B" Series engine for any excess oil splash to run back down into the large ID ventilation neck adapter - From there, we run a 3/4" ID hose down along the engine side and then up to a specially adapted high performance but low restriction custom S&B filter that we use. As you can see, as the connection hose runs down along the side of the engine, it creates a natural "LOW SPOT" that will slowly accumulate any amount of "puke condensate" that may be present in a simple, but 100% effective plastic bottle. We supply a polyethylene capture bottle (about 250 ML in size) and attach it with a very high quality silicone 3/8" ID hose. This particular silicone hose does not require any clamps or sealing compounds whatsoever because of its elastomeric properties of having an inherent soft sealing surface with 100% non-affected stretch memory. Our "T" fitting (has a standard 1/4" NPT thread and is easy to deal with) is installed at this low spot, which is a very important design feature of this or any CCV system. Gravity is free and always present; it should be simple to understand why this natural force should be used to an advantage. Plus, because of the length of our main CCV feed hose, this by itself allows condensing of the pukey gases / liquids due to the natural cooling effect that takes place after they leave the engine. Again, no special or fancy devices needed, all of this is done with just gravity and natural cooling of the gases.
As to the type of main type of CCV connection hose one uses, that is optional-We prefer, and supply, an inexpensive, very flexible reinforced clear vinyl type hose as we like to "see" inside-Just change it out every few years when it gets funky-under 10 bucks at retail level at any marine store or Home Depot.... Just run, support, and "chafe protect" as needed. An oil resistant rubber hose may seem better for some people, but that is the installer's choice. Note: our 15+ years of experience with "oil resistant" CCV hoses that are supplied with other systems has not really shown that they all are "oil resistant" at all.. They not only get soft, mushy, and "sweat oil", but they are expensive to replace. You might check what you have currently to see how oil resistant it really is!! |
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High Performance S & B Air Cleaner with adapter for "Envirovent" |
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Front case breather kit |
Hose and fittings |
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Puke bottle, silicone hose and fittings |
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Factory Vent capped |
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The "Envirovent" CCV system specifically designed for the unique crankcase ventilation requirements of the Cummins "B Series" marine engines. |
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Our Envirovent system is DESIGNED more for the "hands-on" operator who understands his "B Series" engine, its unique requirements as to crankcase ventilation, and his engine room operation in general. Also, this same vessel operator would also desire a CCV system that is long term easy to deal with, does not have the shortcomings as to possible drain valve failures, and other installation issues as discussed earlier, has a low initial cost, is simple to maintain and inspect for correct operation, and is very low cost as to long term ownership. |
Tony Athens | March 1st, 2009
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Our Politics here to help understand "Squeeze Bulb Priming". For sure, I have been using Squeeze Bulbs with diesel fuel for well over 20 years now. I still have not seen one rot or fail externally, so to me they have withstood the test of time in the field. I still get feedback from those who do not have any experience with them worrying about "this and that". All I can say is they are used and approved with gasoline in all types of applications, so to me, they must be safe, regardless if ABYC or some surveyor has an issue with them. If I worried about those things, I just as well quick thinking for myself and go back 20+ years in my work. |
 As to flow and restriction: If you use the typical 3/8" variety squeeze bulb, you can install them in series ( if you like, with no valves or "T's") and not worry about any undo restriction on most mechanical diesels up to 250 HP or so with rotary type fuel injections. On engines with inline or CR "Bosch or Nippon Denso" type fuel systems, I'd use either a single semi-isolated system or a fully isolated system and 1/2" - 5/8" line for the main fuel system as much as possible. With the fully isolated system, you can feel 100% comfortable even using 3/8" clear vinyl hose for fuel line so you can "see" the bulb do its job. Also, when testing fo air, you can allow all the fuel to go through the clear hose an see if you are sucking air someplace before the bulb. |
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SIMPLE MULTI-STAGE FUELTRATIONTM SYSTEM WITH SQUEEZE BULB PRIMING |
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PRIMING SYSTEM CAN BE INSTALLED BEFORE OR AFTER THE FILTERS |
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Nothing I have used does a simpler or better job than the old fashioned and simple "Squeeze Bulb" as to priming the system or using it as a tool to check for other fuel system problems. I'd love to see a 1/2" ID unit, but I have not found one yet... |
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Simple & Effective Isolated Squeeze Bulb Priming System using Clear Vinyl Hose |
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I think the value of this type in installation is 100% obvious to most anybody that has gone through priming a diesel engine in a vessel from both the practical and safety standpoint when you have to get your engine running - In other words, I suggest you just forget about the politics of "squeeze bulbs" that come from ignorant boaters and the typical wharf rat that thrives on "dock talk".
For those who are squeamish about using clear vinyl tubing for this part of the system (Because "no one" has approved it) please feel free to substitute CG A-1 fuel line for the squeeze bulb hoses.
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Tony Athens | January 10th, 2009
Good Question with tons of conflicting ideas on this subject...
One will find that much of the confusion in the marine industry as to Right Hand / CW, or Left Hand/CCW rotation may have its roots based on the early definitions used by the Detroit Diesel Corporation (from just before WWII) in regards to the way they categorized their engines, AND in the way many in the AUTOMOTIVE Industry talk about engine rotation. Although engine rotation is defined in SAE J 824, let’s just say that because Detroit 2-stroke engines were so popular and universal in their base design, (the WW II standard 6-71 block was 100% symmetrical and could be "mirrored" or flipped around/reversed and the output power could be pulled from either end), Detroit seemed to always use the front end of the engine to describe rotation.
Besides that, general "Automotive Lingo" told us that because you could only "see" the front of your car engine, car buffs would use the front of the engine ( the part that they could actually see turning) to describe engine rotation (Right Hand or CW), although car engines actually met the SAE standard of CCW rotation. Totally different than all other manufacturers of engines, air compressors, hydraulic components, etc., etc., etc.. In otherwords, everyone else views "rotation" by looking at the "business end" or "principal output end" of the engine or other appliance / component to describe "ROTATION" direction. And COUNTER CLOCKWISE / "CCW", is the standard of the industry from a Briggs & Stratton lawn mower engine (although the flywheel is actually opposite to the output end) to your VW, Lexus, or BMW, and every gasoline or diesel engine in general use today that may be applicable to vessel propulsion. |
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LEFT HAND, STANDARD OR CCW ROTATION |
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Common Terms Used to Describe Engine or Flywheel Rotation |
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RIGHT HAND, CW, OPPOSITE OR NON-STANDARD ROTATION |
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To sum it up: Whether CCW (standard) or CW (opposite) rotation, it is always defined as the direction of rotation when looking at the flywheel or output end of the engine... See how simple that is !!. |
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As soon as we add a typical transmission behind the engine, the output of the transmission can be either the same or opposite of the engine's flywheel - Hence a "reverse gear" or reduction gear. But not all reverse gears work the same. Years back, even though the Reverse Gear could change the output direction of the engine's output rotation (make the boat go backwards), that does not mean it could transmit full power in either direction. Allison, Borg Warner, and many other reverse gears were only capable of transmitting the engine's full power through one of the TWO sets of internal clutches, and those were called the FORWARD or MAIN CLUTCHES. So, with twin engine boats, opposite rotation engines were developed and the transmission oil pressure system/pump was reversed so it could operate with a CW or RH (non-standard rotation) engine, and use the forward clutch for a left hand prop. That's why we had an Allison MH 20RH and a MH20LH. That's why the BW gears have an oil pump on the front that can be rotated 180 degrees for a different input rotation. That's why on the old Twin Disc MG 512, you could flip over the oil pump and make a transmission work with either input rotation. And that's why a ZF220A has a different oil pump than a ZF220V - Input rotation of the input shaft and/or oil pump direction is opposite. |
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Three shaft reversing transmission |
Right hand prop
Clutch Pack 7, when engaged, connects gear 1 with gear 2 and then to the output shaft thru gear 5 |
Left hand prop
Clutch Pack 6, when engaged, connects gear 3 with gear 4 and then to the output shaft thru gear 5 |
Standard CCW
Input Rotation |
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Standard CCW
Input Rotation |
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NOTE: IN a typical 3-shaft transmission, the RH prop requires slightly less power to spin as the power is transmitted through one less pair of meshing gears |
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Forward - Right hand prop = Input shaft to output shaft
Forward - Left hand prop = Input shaft to Lay shaft to output shaft |
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To understand the transmission a tad more, you have to look at it's basic design what's going on inside as to the POWER FLOW through the gears. In most cases you are dealing with a 3-shaft drop gear (typical ZF63/63A, ZF 220/220A, Twin Disc 5061/5061A , MG 509, MG 514 , MG5114A, etc. - Down angle or not doesn't matter as they are still all 3-shaft transmissions, and the power flow through the transmission is all the same - The power comes into the input shaft and it is always turning the same way (it's connected to the engine flywheel through a torsional coupling) - From there the power either goes directly to the output shaft through 1 pair of meshing gears so now you have the output shaft of the transmission rotating opposite the engine, and with a standard rotation engine (CCW), you would use a RIGHT HAND prop to move the vessel forward, or for reverse output rotation, the power goes from the input shaft to the "lay" or 3rd shaft, and now the output shaft of the transmission is the same as the engine output; hence, you use a LH prop to go forward - REMEMBER, we are always looking from the rear of the engine (or boat) towards the bow or front of the engine when discussing ROTATION, and that applies to props turning inboard or outboard. Just visualize looking through the boat and seeing the engines flywheel (it's turning CCW in a standard rotation engine).
Now let's look at a modern coaxial-type gear similar to a MG506, MG 507, or a ZF 301 or ZF 304. Again, down angle or not doesn't matter, as the power flow through the gear is the same. Coaxial style refers to transmissions when the engine's crankshaft and transmission output shaft are generally in the same plane with no, or very little, drop or offset between them. In a coaxial-type transmission, you have, what I call, a 4-shaft transmission. The power flow is always from the input to the output shaft but through two or 3 pairs of meshing gears to get either rotation of the output shaft. The transmission has TWO lay shafts, per se, instead of just one. |
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Left hand prop |
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Note: In the case of a typical co-axial transmission, the LH prop is slightly more efficient as you are transmitting the powerfrom the engine to the propeller through one less "pair" of meshing gears |
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Right hand prop |
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Remember, we are always visualizing by looking from the back of the boat as if we were looking through the boat & tranmission and could see the back of the engine when discussing "ROTATION" |
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Now that you have this fixed in your mind, ponder these questions - all based upon engine torqueing rotation or how it tends to roll or twist over in the boat under power.
Answers Below, but first a HINT - Remember that the engine will always twist opposite to the load that the crankshaft or output shaft "sees" and that may or may not be the prop!! Let the brain have a little exercise here before you read these. It needs to eat (food for thought) too... |
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1) Which direction does the engine twist when in gear with a standard inline drive? Does it matter if the engine is in forward or reverse? |
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ANSWER: With a convention in-line drive, the engine will always twist opposite the direction that the prop is turning when in gear, be it FORWARD or REVERSE. Looking again, from the back of the vessel, as though the boat were "see-through" and using a RH prop, the engine will rotate or TWIST CCW when in FORWARD. It will twist CW when in REVERSE. |
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2) Which direction does the engine twist when not in gear and the engine is accelerated quickly? |
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ANSWER: When the engine is in neutral, basically the only load it can see is when the engine is revved up quickly (caused by the accelerating inertial of the internal components). Again look from the back of the engine, since the engine ALWAYS spins CCW, then during this rapid "rev-up" the engine will twist momentarily to the right and then remain steady when the RPM's are steady. |
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3) Which direction does the engine twist when connected to a close couple V-drive in both forward and reverse? |
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ANSWER: You do not need to know what is going on inside the Close-Coupled V-drive, you only need to visualize what is happening by "seeing through" the boat. Both the engine and V-Drive are "ONE" (they are coupled together), so the engine / v-drive "unit" will twist opposite to the load (the PROP). An RH prop in FWD, the "unit" will twist CCW, in a similar fashion to a conventional drive with ONE caveat. Because of the much larger offset in-between the crankshaft and the propeller shaft along with a built-in angle between the propeller shaft and the engines crankshaft of usually greater than 12 degrees, this twisting will be "leveraged" to some extent that will typically require a more stout foundation for these types of drivetrains to control this movement. |
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4) Which direction does the engine twist when connected to a REMOTE mounted V-drive in both forward & reverse? In this case I am talking about a V-drive that has its own internal reverse, or is integral to it, similar to a ZF 220V or a Twin Disc MG5114RV. |
ANSWER: With a REMOTE V-Drive, you have a totally different engine reaction, as now, the engine "sees" only the input shaft to the remote mount V-drive (or any remote type of transmission or power absorbing device). The "V" has absolutely nothing do with this part of the question. So, the engine now twists opposite (CW) to its rotating crankshaft (unless the engine has a reverse gear on it before the V- drive similar to a "Walters" unit) regardless of what the "V-Drive" (or other remote mounted device) is doing.
The cardan, or U-joint, shaft is what changes it all because it never changes direction. In a car and your boat, the "absorbing shaft" does change direction. |
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5) Which direction does the engine twist when connected to a REMOTE mounted in-line drive or traditional type reverse gear in both forward & reverse? Believe it or not, although not common, regular type transmissions are remotely mounted away from the engine in some applications. |
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ANSWER: An in-line "remote" reverse gear has a simple answer - Exactly like the remote V-Drive above - The engine will always twist CW when put under load whether the transmission is in FORWARD or REVERSE. |
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6) Is engine twist or torque rotation affected by the internal design of the transmission as to whether it's a 3 or 4 shaft transmission? |
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ANSWER: The internal design of the transmission has nothing to do with which direction the engine will tend to twist. When a reversing transmission is attached or "close-coupled" to the engine (they are an integral unit), you can think of the output shaft of the transmission as the CRANKSHAFT, and the engine will twist opposite to what that output shaft or coupling "sees" loadwise or when the trans is in-gear, be it forward or reverse. |
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7) What is happening to the "remote" V-drive or remote in-line transmission when in forward or reverse? |
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ANSWER: Twisting torque on the a remote V-drive or remote in-line transmission will be opposite to propeller rotation but will be reduced in one direction and increased in the other as the input shaft torque direction is always the same. Calculating exactly what these "twists" would be could be very tricky. Understanding the general concept of what they are is easy. Additional "remote loads" can be or are fwd/rev thrust, and fore/aft rotation which is opposite/90 degrees to the propeller torque axis, but this is all dependent upon mount design, gear ratios, etc, etc... Also "down angles" add a new dimension to it all. Gets very complex and that is the biggest reason why a remote mounted V-Drive requires engineering expertise for the installation to be long term reliable. Ever heard of the "V-Drive stigma"?... |
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8) And the toughest of them all, if you like scratching your head - Think about engine twist in a car with a conventional front engine and rear-wheel drive in both forward and reverse. Then add some flavor and ponder that with front wheel drive... |
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ANSWER: No answer from me on this one as we all need to feed our brain. |
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I hope this helped some to set the record straight and to remove some of the confusion on the subject "Which Way Does My Engine Turn". |
Tony Athens | January 1st, 2009
When looking through engine literature and talking with sales people, often times the term "continuous duty" is brought up to help make a point or even sell one product over another. Here's my perspective on the subject.
Let's take all the "color" away from the question and just look at what most manufacturers mean by the word "continuous" in the more accepted vernacular of the commercial marine or industrial industry. If I may summarize this (I will try to be accurate and colorblind), I believe it goes something like this (with a few wording variations from different manufacturers):
Uninterrupted service at 100% full rated power for an unlimited number of hours per year - In other words, the engine was designed AND rated for "pedal to the metal" 24/7/365, and this is the way I understand a true "continuous duty rated engine" or any appliance to be, AND give an acceptable life when operated like this. But know this; there is at least one popular engine manufacturer in the marine recreational market that has a very different definition of "continuous". Seems Yanmar will rate an engine at, say, "maximum output is 480 HP at 3300 RPM" and on the next line say that the same engine has a "continuous output at the crankshaft" of 436 HP at 3198 RPM (about 70 hp per liter). What that actually defines has left me befuddled for about 20 years. I truly have no real clue as to what Yanmar actually means by that, and I've been a dealer for the product (over 10 years). Plus, all the while they have such strict guidelines as to operational hours per year. Makes zero sense, and I have no plausible explanation to this way of describing the word "continuous" as per Yanmar. Maybe someone else can add some reasoning to this that can explain Yanmar's take on this. Or, I guess I could leave it as a clever marketing tactic.?? |
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YANMAR 6LYA 370
CONTINUOUS -
55.9 HP / LITER |
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In general, current engine design technology (I am talking 2008) allows an upper end of about 35 HP per liter on a high speed diesel engine (that's a diesel classification of actual piston speed, not RPM (even though I am using continuously 1800 RPM rated engines for this discussion) up to about 60 liters of displacement that would have a rating like this, along with a consumer accepted reasonable life. Believe it or not, it is the consumer (his wallet) that really sets an acceptable standard as to engine life, and with today's technology, I'd say that acceptable life needs to be in the range of 8000-16000 gallons of fuel burned per liter of displacement before we are at "TBO". This fuel number is also based on a CONTINUOUS duty rated engine that is run in an overall duty cycle at 50-100% of its rated HP. Lower duty cycle = more fuel burn per liter ..... that's one reason for the wide gallon per liter window size, and another is that more iron per rated HP seems to translate into more engine life per fuel burned before TBO.
Now you ask, where did I come up with 35HP per liter. I didn't, but if you search through all of the latest high tech diesels made by MTU / Detroit, CAT, CUMMINS, VOLVO, MAN, SCANIA, IVECO, JOHN DEERE, MITSUBISHI, etc., that actually go after the workboat market and really understand what continuous duty means, you'll find that the UPPER limit is about 35HP per liter (about .6 HP per cubic inch - if you do some research, I think the Cummins QSK 19 at 660 HP is about as high as that number gets). But MOST continuous duty rated engines are actually below that number (20 to 30 HP per liter).
So, what could all of this really mean to people in the recreational marine market when we only talk about engines that are rated to 60 - 80+ hp per liter? Actually, not much because if the boat builders sold engines with this type of engine with a "de-rated HP output", most of the boats they sell would never make it over the hump on DEMO day and would never sell. Performance sells the product, not engine longevity on sea trial day. |
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YANMAR 6BY 260
CONTINUOUS -
66 HP / LITER |
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But you could also look at this subject the way we think you should when shopping performance (put initial looks, gingerbread, and creature comforts aside for the time being):
Being applicable to this discussion and the point I am trying to make: Take any modern (mid 90's and newer) 4-12 L diesel rated at 60-80 HP per liter (80+% of all the engines we talk about here are in this class), and YOU want to do it right. This is how I think your engine should be selected as to HP & size for your application.
Be sure that you are happy with your vessel's performance set up the way you will actually be using it (that means loaded with all you need to meet your application goals) burning no more than 2.2 GPH per liter at your happy cruise speed operating at a 30-50% duty cycle or less if you want a chance of seeing 5000 hours. If you need to burn closer to 2.5-2.6 GPH gallons per liter to get you up to the speed you need to go, you must accept a much lesser engine life (IMO, in actuality you may be borderline underpowered), and you may not see 2500 hours before your engine is history. I'll bet the sales broker never talked along those lines - seems the only thing they know about diesels is something like 10,000 hours when the subject engine life comes up. If during this 2000-5000 hours you are propped to where you cannot reach rated speed or more, then the numbers will be even worse.
Don't believe this? All you need to do is ask yourself why so many of today's modern small diesels are sold on the used market as "rebuilt", or need rebuilding with such low hours. Keep in mind that if you run at 2+ GPH per liter or more, a simple problem (lose a coolant pump belt or impeller) that occurs running on the "edge" becomes a major issue compared to running that same engine at 1 GPH per liter. When you only have a 1400 - 2000 lb engine/trans package cruising at 2 GPH or more per liter, you have no time and no room for even the simplest overheat issue that might be caused from losing an impeller, engine coolant pump or hose.
I could go on and on with this (actually I have in some past articles and postings). Regardless of how HP has gone up per liter over the years and the quality of the base product has gone up with it (it really has), you'll find that these numbers are where you need to be if you want 10-15 yrs of engine life running 200-500 hrs/yr in recreational service in the typical planing boat that is sold for its "performance" qualities on plane. But take that same boat, get realistic about how fast you DON'T need to go, bring it down to hull type speeds and run those same engines at 10-20 HP per liter when traveling for hours, care for all as if these engines were your passion, and 10,000 hours and 20+ years of great service is very do-able if you follow all that I preach about in these forums. From here it's your call as to what you want to believe and do. But if nothing else, do remember this when you shop - if you are not performance happy for cruising to your favorite 60-80 mile fishing reef at 2-2.2 GPH per liter or less PER ENGINE and expect to do that 25 times or so per year for 10 years, don't expect your engines to meet that 10 + years life and 5000 hours no matter how often you change your oil. |
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Our Winner and Current Champion in this "Continuous" Horsepower Race |
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YANMAR 6LY3
CONTINUOUS - 75 HP / LITER |
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From here it's up to the operator as how they want to think about their engines horsepower rating. |
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An Interesting Side Note |
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The Cummins QSB 5.9 is a super popular engine and I feel should be addressed here. Cummins or CMD has never rated it as a "continuous duty", and I don't really know why other than the market, has not needed it. They offer it in a "Heavy Duty" rating at 230 HP at 2600 RPM which is really very close; 8 hours out of 10 hours at WOT - Not bad and obviously they feel very confident about the quality of what's inside. If was I was going to interpolate all I know about this engine and give it a 24/7/365 rating, I'd be very comfortable at either 165 HP at 2100 RPM or 155 HP at 1800 for a true continuous rating. Seeing 10,000 ++ hours before TBO time & run at a 50%-75% duty cycle at these rating should be a piece of cake if you treat all the rest right. |
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Rated 155HP @ 1800 RPM = 26.7 Hp / liter
Rated 165HP @ 2100 RPM = 27.9 Hp / liter
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Just remember this when you read thru my thoughts on this subject: You need to be sure to keep all in the context of understanding "Cruise HP" and where all of my politics on the subject come from.
You need to understand "duty cycle" in its simplest form - there is a big difference in a 35%-45% duty cycle, compared to under 30% which is a recreational guideline by many manufacturers that seems impossible to meet if you fish 12-16 hours days 60-80 miles from shore, make long trips mostly on plane, AND / OR cruise at close to manufacturer's CRUISE RPM's which is usually 200 off the top.
It goes like this (typical 12-14 hours engine time example on a 370 Diamond that travels at 18 - 20K's loaded for bear and fishes 80 miles from home): |
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Actual fuel consumption during 12 hours engine time |
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12 hours of engine time at WOT fuel consumption |
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201 GPH x 12 Hours = 402 gallons |
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Actual fuel consumption on example trip for 12 hours engine time= 155 gallons |
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Duty Cycle= 39% |
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Overall though, I think the biggest problems are with the boats/engines that have changed owners multiple times over the first 300 hours spread out over 5-8 years. These are the engines that seem to be in the worst shape because real history of "who did what" is never available or known. Lots of sitting, lots of fast throttle jockey sales broker trips to show off the "new boat" and very little of the real maintenance needed as the hours are so low on the engines. Ever see an owner's manual talk about "Marine Age". |
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CUMMINS 4B 3.9 |
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CONTINUOUS - 13.3 HP / LITER |
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JOHN DEERE 4045 |
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CONTINUOUS - 20.0 HP / LITER |
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JOHN DEERE 6068 |
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CONTINUOUS - 27.0 HP / LITER |
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CUMMINS KTA 38 |
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CONTINUOUS - 28.9 HP / LITER |
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JOHN DEERE 6125 |
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CONTINUOUS - 30.4 HP / LITER |
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CUMMINS 6CTA 8.3 |
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CONTINUOUS - 30.7 HP / LITER |
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CUMMINS KTA 19 |
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CONTINUOUS - 31.6 HP / LITER |
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CUMMINS QSK 38 |
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CONTINUOUS - 31.6 HP / LITER |
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CUMMINS QSL |
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CONTINUOUS - 32 HP / LITER |
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CUMMINS N14 |
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CONTINUOUS - 32 HP / LITER |
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DETROIT / MTU SERIES 60 |
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CONTINUOUS - 32 HP / LITER |
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CUMMINS QSM 11 |
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CONTINUOUS - 32.1 HP / LITER |
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CUMMINS QSK 19 |
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CONTINUOUS - 34.7 HP / LITER |
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* VOLVO D9 |
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CONTINUOUS - 31.4 - 37.7 HP / LITER
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* VOLVO D12 |
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CONTINUOUS - 24.3 - 37 HP / LITER
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* NOTE: Volvo has multiple continuous duty ratings at 1800 RPM and they are definitely at highest end of the true continuous duty spectrum. |
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Realize that I am a very conservative guy as I always add in the "Marine Factor" when I talk about engine loading, and to summarize, it would go like this:
"Marine Age" is something that seems unique to a diesel in a boat - Without even using the vessel, the engine slowly goes south, especially if all you do is change oil and zincs per the maintenance manuals.
Many or most vessels are over propped to some extent in that they do not even reach rated RPM, especially during the new owner's "learning curve" which can be years and 100's of hours later spread out over a few years. By the time the engines RPM's are where they need to be, you have already stressed many parts of the engine well beyond its actual hours.
The salt water cooling system of the engine is just not that tolerant of the typical maintenance that is specified in the owner's manuals or is taught in the certification schools by the engine distributors. I speak from many 1000's of dollars spent on both Cummins and Yanmar schooling over the last 15 years, and neither one has a clue about what it takes to really care for a SEAWATER AFTERCOOLED diesel engine making upwards of 60HP / liter - Read your manual as all they seem to print is "change your impeller, replace zincs, and keep the weeds out". Want your very expensive seawater system (which is also the life blood that keeps your engine from having a "thermal melt down") to last 10+ years on a light weight high speed diesel? You'd better plan on getting much more involved than that, and start when the engine is still young "marine age wise" and not just engine hour wise.
And last, I am not probably being totally fair to some of the newer technology out there (Common Rail Engines for instance). For sure, the loads on the internal components must be less per HP produced because of the smoother combustion process (not just one nuclear type explosion) with each piston down stroke. So maybe we could add 5-10 % to cruise HP per liter and we could still sleep well at night. But on the other hand, I am not at all that comfortable with super light weight 3600+ RPM diesels converted from automotive use to marine use, and have no industrial, commercial off-highway, truck, or other market history that can show how tough they really are in other uses.. Driving the Autobahn at 80-100+ MPH has nothing to do with traveling at sea in a planing hull pushing into head seas and 10+ K's of wind.
So remember, work all of this into the equation when you decide how many ponies you want to pull out of your investment traveling from Point A to Point B for hours on end, versus amount of years you want to keep those engines running, performing as if they were close to new, and that investment is still paying dividends in the form of an overall reasonably low cost of ownership. |
Tony Athens | November 1st, 2008
For the Cummins B's and C's there has been what I consider, a high failure rate of the of idler pulley on the front of these engines. What's actually failing is the center 10mm bolt (hex head cap screw) as it is shearing off at the bracket. This goes back at least 6 yrs and the factory has made a couple of changes, but from my view has totally failed to fix this reoccurring problem.
By viewing images within the article, you'll see the difference between the new parts vs the old parts. I think the intent of the engineer that was assigned to this upgrade was to increase the surface area of the spacer where it is tight up against the bracket, additional support and lessening the leverage. All he did was change the diameter just behind the bearing and DID NOT change the footprint of the spacer where it needed to be enlarged. This is another example of true "couch engineering". I tried to give some input to the factory about 10 years ago as to what needed to be done and the factory guy that was at my shop agreed. He even said "why such a cheesy bolt size, couldn't they just use a larger bolt". That is a very accurate quote as far as the content of what he said. So at this point I decided to start doing the pictured upgrade.
Replacing the 10mm bolt with a Grade 8 - 7/16 x 2 3/4" bolt and nut. This requires drilling the spacer (new or old style) to 29/64" and drilling the engine bracket to 7/16". You can either reuse the front washer by drillings it to 29/64" or use a new 7/16 high quality flat washer in it's place (much easier). For the newer engines, you have to remove the sheet metal cap (like a thin freeze plug) to gain access to the bolt. You do not need to replace this and I recommend that you don't. The newer looking pulley doesn't offer any advantages from the longevity stand point and I'm not sure what the factory's reasoning was for the change. Both pulleys use industry std 6203 sealed bearings (worth about $ 8 ea or less) and can be changed with minimum effort if this is needed (about every 5000 hrs in a dry environment). When doing this upgrade, be sure you lubricated the parts/bolt/nut and torque to yield (about 45-55 ft lbs).
Actually, I made a judgment error about a year ago when I first saw the "new" spacer/kit. From a casual look I figured that indeed the factory enlarged the footprint of the piece and decided to not make any more "unauthorized" upgrades. I didn't actually measure it and allowed at least 30 engines to leave my shop without the "in house change". NOT any more, as although I don't know of any failures of these engines, I do know of some others with the re-designed parts. |
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Original Parts from about "1988" engines. |
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Old vs. New disigned Cummins parts - To this very day about 10 years later, I still cannot figure out what Cummins was thinking. |
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The real long term solution - A Grade 8 - 7/16" bolt / old spacer style or new, makes no difference if you upgrade the bolt size. |
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Back to drilling. I recommend this procedure for any B & C over 2 years old and also for any new engine in a single engine boat.
The spring idler assembly has also had a few upgrade over the years, but none of these were from failure problems. There has been some casting changes, spring rate modifications, and ???. The good news w/ the tensioner is that it costs less than 10 yrs ago by a substantial margin. The current # is 3936201 and it's about $100 or #3934818 , about $90. This belt system has proven to be a good reliable system (other than this idler pulley bolt) with belt life typically at 2000+ hrs. With a little effort, even that problem can be solved. |
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The two hard parts of the project that you need to do. Bore out the "spacer / bushing / sleeve" (what ever you want to call it), and drill out the bracket to accept a "real bolt". |
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Finished Repair / Bored spacer, a 7/16" Grade 8 bolt & Nut. Assembeled with some grease and torqued to about 45-55 ft lbs - Done right, no issues ever again !! |
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Note: I have resurrected this article from about June 2000 era as I am now seeing the issue re-surface again with the new Cummins REMAN Marine engine packages. Could they have gone backwards ???
We've recently released a solution to this problem, take a look at our Idler Pulley Upgrade Here
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Tony Athens | October 1st, 2008
Since understanding oil pan capacities & their relationship to "dip sticks" seems to be an ongoing topic of discussion, I will attempt to explain what it really means.
What is most important to remember or understand is that oil pan (sump) capacity is exactly that, and HAS ZERO to do with oil filters, oil lines, oil coolers or ?? The second most important part of understanding oil capacity is to realize that the dipstick measures OIL PAN capacity and it has NOTHING to do with the oil filter being full or not, and/or any other oil in the system which is part of the "total system capacity". "System Capacity" is that amount of oil in the pan (the dipstick measures that), and all of the other oil that is in the engine (oil filter, lines & hoses, oil galleries, etc.) that cannot be drained from the oil pan under normal circumstances. |
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Cummins 330/370 Diamond with late style reversible screw-in locking dip stick. Cummins changed the marine oil pan design for this engine about 2002 (maybe the 4th time now since 1985 when they released the Marine version of the 5.9 B series) to include better internal baffling (helps to mitigates "oil windage"), and came up with a new designed reversible and locking dip stick - Nice improvement and is standard on all of the REMAN Marine B's as well !!!! |
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Understanding the basics in changing oil and having a correctly marked dipstick is very simple. Drain the oil pan completely, add the correct amount of oil to the pan listed in the chart (LOW mark first). Wait a couple of minutes & check your dipstick a FEW TIMES to be sure it is correctly marked for the LOW MARK - If not, then remark it correctly. Then add the 1-4 quarts listed and check your HIGH MARK. If you change your oil filter, it's always best to fill it first (no dry starts wanted) and you are done. If your filter was installed empty or dry, after you start it, the oil level will be slightly below the high mark as some oil in the pan was used to fill the filter. If you pre-filled the filter, then the oil level in the pan will be as it was (or very close to it) after the start-up and fill. |
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Pictures of correctly, and incorrectly, marked dip sticks. The upper scallop notches were done by a "Cummins Tech" who had no clue. Not only did he add 2-3 gallon too much oil when he marked them, the notch he put would surely cause the dip sticks to eventually fatigue and fail. The lower X's show the CORRECT OIL LEVEL, and done per the book using some common sense. These are from a QSM that has seen more than its share of dip stick issues over the years. Somehow, I always thought the dip stick was a simple part of the overall engine design ???? |
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And last, running your engine on the low mark has NO detrimental effects on the engine, and in the case of a B series Cummins that uses the very shallow marine oil pan, this is a recommended practice from us to help alleviate or keep oil "whipping" to a minimum.. In general, and from a personal point of view, we prefer keeping the oil level in the oil pan in-between the "marks" on a correctly marked dip stick on all engines regardless of the color. This also applies to transmissions and/or gear boxes. |
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Listed below are the factory oil capacity numbers for the popular Cummins marine engines. |
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Popular Cummins Marine Engines |
Oil Pan Capacities (quarts)
Dipstick marks |
Oil Pan Capacities (gallons)
Dipstick marks |
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Low |
Hi |
Low |
Hi |
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4B / 4BT / 4BTA 3.9 |
9 |
10 |
2.25 |
2.5 |
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6B / 6BT / 6BTA 5.9 (includes 330 / 370 Diamonds) |
13 |
15 |
3.25 |
3.75 |
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6CTA 8.3 (includes 450 Diamonds) |
14 |
18 |
3.5 |
4.5 |
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QSB |
13 |
15 |
3.25 |
3.75 |
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QSC 8.3 |
14 |
18 |
3.5 |
4.5 |
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QSL 9 (deep pan) |
16 |
20 |
4 |
5 |
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QSL 9 (shallow pan) |
14 |
18 |
3.5 |
4.5 |
QSM 11
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28 |
32 |
7 |
8 |
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QSM 11 (Rear Sump)* |
30 |
34 |
8 |
9 |
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QSM Oil Pan |
So the way I see it...
Start with a 100% drained oil pan...
Dip Stick Option on SEAWATER PUMP side (usually starboard motor): Add 8 Gallons and mark LOW. Add 1 more and mark HIGH
Dip Stick Option: on Exhaust side (usually port motor): Add 9 Gallons and mark HIGH) - 8 Gallons may or may not show at the bottom of the stick, so as long as you see any oil on the stick you have at least 8 gallons.
So simple even a Fisherman can figure it out!!
Tony Athens | August 1st, 2008
There seems to be a lot of misunderstanding in the industry as to the correct fuel line sizes to use for various engines when repowering a boat. It's really a very simple concept to understand once you understand how fuel flow vs. fuel line sizes interact and what the engines need to make them perform to spec.
Because of the popularity the 6 cylinder 6BTA or 6CTA Cummins (not that it really matters), we'll use these engines as a basis for this discussion. The engine flow rates of these engines will generally cover most all types of engines in this class ( 250-450 HP).
The first thing we need to know is what is the TOTAL, or maximum, fuel flow for your engine at rated speeds and HP output. In this case, and most any 250-450 HP 6 cylinder diesel that uses an ND EP-9 type or Bosch P7100 fuel injection pump (or a system of similar design), just assume the fuel flow is about 1 GPM. Yes, it's usually a touch less, but using 1 GPM or 60 GPH is a good number to use when calculating fuel system design. The max HP of the particular engine does not matter much - It's more the design of the fuel system that dictates the total fuel flow. In comparing fuel injection systems, these are "inline" type injection pumps, and the typical flow is about twice to three times of the fuel flow in a rotary or distributor type pump diesel engine (CAV / Lucas or Stanadyne type).
Next, we need to know the factory's maximum values, numbers, or pressure drops that the engine can tolerate to work properly for both the supply side (suction) and the return side (restriction-pressure of the return line). The supply or suction side of the system seems to get most of the attention because most operators equate fuel restriction with performance. Yes, you can equate the two but not as most think. We'll get to that later as that is a slightly different subject.
Fuel supply restriction or "pressure drop" is always measured as a negative number because it is on the suction side of the fuel lift or supply pump. Units of measurement can vary, but inches of Mercury (Hg) seems to be most accepted. Regardless of the units of measure used, fuel restriction values need to be very low, and in a general sense, the lower the better when the system is fresh or new as this gives the operator more time between filter maintenance. Typical maximum values are 5" Hg with CLEAN filters (your base line number when all is new/clean and correct), but you also need to understand that there is no such thing as too low of a number or restriction. Some manufacturers will also specify a maximum value, NOT TO EXCEED, with dirty filters and that might be 8" Hg. Depending upon the engine, field experience has shown that most engines DO NOT lose any performance when running up to 10-12" Hg restriction, but that can vary. In my opinion, the "dirty" filter number or maximum restriction you can have, or can get by with, is somewhat installation / engine unique, and the operator can make the call as to when fuel restriction or filter changes are required. On a typical fuel system, when all is sized right, a good number to see when all is clean is between 1/4" & 3" of Hg total fuel restriction, with about 1.0 to 2" Hg most common in a well designed fuel system. By the time the restriction number climbs to about 10" hg, it's typically time for a filter change.
Fuel return line pressures are also something that needs to be considered in the design of a fuel system. Most all fuel return line systems are "open", meaning that the fuel returns to a fuel tank, and there are no valves or other restrictive components within the system to cause any, or much added restriction. Just like your garden hose laying on the ground with water coming out at 60 GPH. So, where could the restriction come from, you ask? Some may come from an inline return fuel cooler (not much if they are sized right) and friction inside the fuel line with fuel flowing thru it, which brings us to what this discussion is about - Fuel Line Restriction, and how it interacts or affects overall fuel restriction on both the supply and the return fuel system on a diesel engine.
Just about everybody seems to equate fuel restriction with the fuel filtration system and it's design, and never thinks about the fuel line as being a major factor in this equation, even when all is new and clean. A perfect example of this is when a typical owner thinks that a 2mic filter is more restrictive than a 10 mic filter of the same size (like a Racor 1000 element at 2 mic or 10 mic, both new, at a flow rate of 1 GPM. In actuality, both elements would be under .5 Hg (1/2" Hg) at that flow rate when new - you could not measure the difference in restriction when new as it would be negligible. Yes, the 2 mic will load quicker (get dirty) and the restriction would rise faster, but isn't that what it should do?.
But, here is what all seem to not realize. Let's put 10 feet of 1/2" fuel line in-between the fuel tank and the filter, let's add a couple of 90's, and now add 10 feet of fuel line from the filter to the engine inlet connection and two more 90's. Pretty typical in a 35-40 ft boat as to fuel line routing... Let's take our 1 GPM w/ #2 Diesel and do a "fuel line restriction calculation" based on typical values of #2 at a temp of 100 F. I'll use a specific gravity of .85 and a viscosity of 3.0 centipoises (these would be reasonable numbers). We just ended up w/ a .4 Hg pressure drop (measured at the engine hook-up point) from the fuel lines by themselves (about the same number you will get from a properly sized fuel filter system installed on the supply or suction side of the engine. This would be about normal. Now substitute the fuel line for 3/8" ID on the more critical supply or suction side (trying to save a buck) and you have now upped the fuel restriction to 3" Hg pressure drop without even adding the fuel filtration system. Inside the ½" fuel line the fuel would be traveling at 2 ft/second and inside the 3/8" fuel line just over 3 ft per second. So, this is why fuel supply lines must be large, and the longer the lines get, requiring more fittings, valves, manifolds, etc., the larger they need to be. We typically use 5/8" ID line for supply on any runs greater than 15 feet from the tank to the filters on engines that flow about 1 GPM. Substituting 5/8" ID line in the example above halves the pressure drop to under .2 Hg.
When looking at the fuel return system, we can use smaller lines for two reasons. One, the maximum allowed value for the pressure drop is usually 2-4 times more and the return flow is always less (at least to some extent) than the total fuel flow. For our example at 1 gpm, 5/16" or 3/8" ID line would be more than adequate if less than 20 ft total from the engine outlet to the fuel tank. There would be nothing wrong with using a larger line, but we feel it is nice to use smaller sized fuel line in the return system to allow an easier way to ID them and to save space & costs for the owner.
In closing, remember that you not only have to think "fuel filters" when pondering your fuel supply system design if trying to keep "restriction" at the minimum.. Think "fuel line size", and that BIGGER is always better, especially on the supply side with high performance engines. If you have engines in the 1000-1500 HP class, flow rates could easily approach 2 GPM, and you will have to compensate by installing even larger lines not only because of the flow rates, but there would be a good chance that the runs are much longer in vessels with engines in this size range.
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Custom "Last-Chance" final high performance filter set-up for Yanmar 6LYA with "larger than factory" fittings and hoses. |
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Flow-Scan addition required going to 1/2" ID Hose and SAE #8 fitting although the engine "usually" uses and come factory set-up for 3/8" ID fuel line. |
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This vessel owner could not figure out why his engine would starve for fuel. He had used 1/2" ID fuel line for all but forgot about his "old" pick-up tubes. |
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Very old fuel manifold system done a mix of iron and brass fittings. Although kind ugly and a touch complex, it was low on restriction because of ample sizing (mostly 3/4" pipe size) of all the fittings & hose sizes. |
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Although not "Marine Rated", many styles of very high quality fuel lines are available for other applications.. Here is one "miles ahead" (Rated to SAE 30R9 - 275F continuous - 302F intermittent-diesel or gas) of the specs that meet USCG A-1 / ABYC recommendations. It's so typical that marine certifications are way behind new thinking and design - "Fluff", politics, and old fashioned ideas seem to take the center stage so much in this industry that many times we just march by our own drum when we see something that offers a better way to accomplish the task. |
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A simple and low restriction manifold system using large full-flow valves and 1/2" ID lines for a 2 x 300 HP engines and 1 x 30 Kw gen set that was done by the owner with a touch of guidance. |
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Custom manifold is gravity fed with 1.25" ID hose from the forward main fuel tank 30 feet forward of the engines. This manifold feeds 2 x QSM 630's and 2 x 20Kw gensets with #10 hose for the main and #8 hose for the generators. |
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Although not part of the fuel supply system after the tanks, this was a fuel fill hose on a 46 Bertram we re-powered. I think it was time ... |
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Multi-Stage system with back-up for mains - All #10 hoses and fittings to the filters for "basically" no measurable fuel restriction between the filters and the fuel tank. |
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Ultra-low restriction Multi-Stage "FUELTRATION" system for those who want the ultimate in delivering the cleanest possible of fuel to their engine while monitoring filter loading on an individual basis - Continuous flows to 100 GPH are no issue with this system and dealing with old dirty tanks is a cake walk, while offering simple and low maintenance intervals for the vessel operator. |
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Tony Athens | August 1st, 2008
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Fuel coolers are part of the typical fuel system on most marine electronic engines and are also used as a factory installed option on many non-electronic engines. It's obvious they are there to cool the heated fuel return flow, but try and realize the actual purpose of why the heat, or EXCESS heat, needs to be removed. We think that fuel cooler application and use should be looked at with an understanding of the system, the "why and the how", thus enabling you to make an informed decision as to whether or not you need to cool your fuel. Remember, we have a saying for all marine applications - "One Size NEVER Fits All". If you understand the system, then an informed decision can be made for your application. |
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Understanding why "Cooler Fuel" can be beneficial: |
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Cooler fuel equals denser fuel which can translate into more HP that is available from the engine. |
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Cooler fuel, or a more stabilized temp will assure that as the day gets hotter and the fuel tank volume gets lower, you do not see a decrease in MAXIMUM available HP - Notice I said MAXIMUM HP. |
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Comfort - Imagine having fuel tanks under the floor, especially in a salon area at 140F on a hot summer day. |
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Safety & component reliability and longevity - I doubt you could find a study documenting this, but I'd certainly guess that fuel lines and filters would last longer with 90F fuel passing thru them vs. 140+F fuel running thru them. |
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In the case of Cummins Electronic engines & probably some others, (both Common Rail, "CR", & EUI systems), the supply fuel is used to stabilize or control the max temp of the on-engine ECM - The fuel supply passes thru the fuel cooled heat-sink that the ECM is part of - Liquid cooling per se ........ Cummins has a MAXIMUM SUPPLY temp measured at the inlet of the engine of 140F for their electronic engines (160F for the mechanical engines). That may not sound very cool, but it's cool enough to ensure the ECM has a stabilized temp below what they want to see to assure longevity. But, since rated HP (WOT, full load) is measured at a much lower temp (maybe 70-80F-ish), I doubt you would achieve rated HP on 140F fuel being fed to the engine. |
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The real impetus to this discussion was about "removing the cooler" and if this could be done. Actually, we remove many fuel coolers on both CR and EUI engines in our work (well over 100 electronic engine installations in the last 5 yrs) and have no issues whatsoever, but you must understand this is 100% application specific. |
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Most of our work is commercially orientated and many of the vessels we deal with have very large fuel tanks (100's to 1000's of gallons), and thru normal course of circulation, excess heat is safely and comfortably dissipated thru the surfaces of the tanks (like air cooling or thru conduction & convection). |
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Many of these vessels have integral fuel tanks so a fuel cooler is built into the boat. Think of it like a very large "Keel Cooling" system. I tend to think most steel vessels are built this way regardless of the actual use of the vessel. |
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Just about all of these vessels cruise at very low HP levels in relation to the HP that is available from the engine. Or, we may install an engine with a much lower rating than the recreational equivalent (maybe a QSM that could be rated at 670-715HP, but we install the 350HP version). Example, an engine rated at 540HP, but which cruises at or has extended running never exceeding 150HP (about 7-8 GPH), would never need a fuel cooler for "Horsepower" reasons as this would preclude that the operator would NEVER notice any decrease in HP even if the fuel supply approached 140F. |
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Cummins (and I'd guess most manufacturers) have a max fuel supply temperature NOT TO EXCEED. How you control that fuel supply temperature is not written in stone, at least with Cummins as it's merely a specification or requirement that needs to be met - With Cummins, the fuel cooler option does not have to be included in a factory ordered engine in many cases - It can be left to the OEM or end user to decide how he can meet the spec and the application needs. |
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The factory installed fuel cooler for the QSM causes much grief in many installations due to it's location on the engine. It's total overkill as to size, and IMO "what were they thinking" comes to mind. Over the years, we've seen an extraordinarily high internal failure rate of these coolers as well, which are produced by a New York based company doing business under the name "CHAMP"... Not a good sign !! |
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QSM sans the fuel cooler. Not only does it make for an easier and cleaner installation, now you can easily swap the inlet elbow 180 degrees to allow water to come in from the other end.. Installing a much smaller fuel cooler (maybe a2" x 6" unit if needed) is super easy using an auxillary seawater feed such as you would use for your dripless shaft seal (3/8 or 1/2" hose size). |
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From our point of view, if a fuel cooler is not needed and the engine manufacturer specification for fuel supply temperature can be met under any condition (most adverse or worst case scenario), then remove it and you will also remove unneeded plumbing and hardware from the engine, besides removing the risk of losing a fuel cooler from an internal failure - Yes, we have seen many of them fail, some with disastrous contingency damage to the engine. As to our own Seaboard SPEC - We shoot for 120F as an absolute max in an application where we know it is not needed for any of the reasons mentioned above. |
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Ponder this regarding the need for fuel coolers - just because a "CERTIFIED" tech or the mechanic you hired has not seen a CR or any electronic engine without a fuel cooler just tells me he has more to learn, and needs to understand just how and why they may or may not be needed. Do we ever leave factory fuel coolers in place? Of course we do, but again, it's 100% application specific. |
Tony Athens | August 1st, 2008
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And I thought you knew all of this stuff - Tons already written on this site http://boatdiesel.com/ about fuel filtration, gimmicks, and the like - many individual postings, a few very long threads, and a few good articles. |
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Custom SEAMAX FUELTRATION TM system for polishing, priming, and transferring fuel put together by the owner who was tired of clogging his Racors every 8-10 hours. |
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But in a nutshell, "Algae-X" and "Fuel Mag" are some of those "magic magnet" contraptions, "RCI" is one of those "spinning" devices, and Multi-Stage Fuel filtration is filtering in series with progressively finer filtration from large to small ( maybe 30/20, 10/7 and 3/2 mics) . No "gizmo's" no "magic," just proven mechanical filtration using the most modern filtration product available.
BTW, if you are into fuel "gizmo's", this link is a winner...http://www.epa.gov/otaq/consumer/reports.htm
And more important, there is NO such thing as "too much" or "too clean" concerning diesel fuel filtration when one really thinks about it. All you have to do to confirm this is to do some injector seat inspections at 2000 hours on some good running engines. This will tell you who has the minimum fuel filtration that gets by, and the ones who really have clean fuel.
The Overview of the Marine Fuel System
Because of the changing requirements of the modern "Common Rail" fuel systems that are showing up w/ the new Tier 2 marine diesel engines, it's time to revisit this subject to be sure ours readers have the most up to date and field tested information available to protect their investment. Much of the information below has been part of other postings and small articles I've put together, but I thought it would be best to try and bring some of the older info into this and blend it in with some new ideas and information. I would also like to point out that all of this information is derived from a conglomeration of 10's of thousands of hours of field operation, 100's of thousands of gallons of fuel filtration with our proven systems, and from keeping up on the latest requirements and data from popular engine and filter manufactures. |
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Commercially proven Multi-Stage System meeting strict common rail fuel requirements - 20 year old fuel tanks, 1000 hours later, approx 60,000 gallons of fuel thru these filters, and ZERO issues |
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There are some very important points to understand about the overall selection of YOUR filtration system, and listed below are some of them that seem to be the least understood and may require some additional thought before you make the choice: |
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The Total Fuel Flow of your engine-not just the max rated fuel burn. It's real typical to have a diesel engine rated at 300 HP (16 GPH max fuel consumption at rated WOT) but have a fuel flow of 60 GPH-1 gallon per minute ! Your entire fuel delivery and filtration system needs to be sized for the max fuel flow and not just maximum fuel consumption. |
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The Tankage or Holding Methods your vessel-older fuel tanks will typically have something in the fuel tank that that you do not want your engine to burn or get anywhere near the "on-engine" or last chance filter that is part of the engine fuel system. Whether it is be some type of growth (algae), accumulated "mud" (diesel fines, sludge build-up, etc), rust flakes (from older steel/iron tanks), water, internal tank coatings that are deteriorating, or ???, there is always something in there that should not make it past your OFF-ENGINE / PRIMARY fuel filter system. Remember this for later. |
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Your Application and Use - Using your vessel for the weekends and making 150 mile round trips 10-20 times a year is very different than working your vessel 20 days a month 10 months out of the year. Big fuel burners will typically need larger capacity fuel filters to keep maintenance intervals to an acceptable level, but anyone will benefit from more filtration capacity as it will eventually pay dividends by not clogging as easily when you (finally) get that lousy tank of fuel. |
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The Fuel Injection System Requirements of your engine - Every manufacturer of diesel engines have certain MINIMUM requirements for the quality of the fuel that is fed to the engine. Cleanliness is next to godliness when we talk fuel injection as there is no such thing as "too clean".. So, after spending 10's of thousands of $$ on either a new boat or a repower, why would not spending a few $100 more by upgrading the "minimum" of fuel filtration equipment that is typically part of the supplied equipment list in just about every boat I see, not be a wise investment? Adding an additional layer of fuel filtration protection and using the most modern filtration media available will always be the best money spent for long term reliability for any fuel supply system on a diesel engine-and that applies to your truck and RV too. Things have improved much since the days of cellulose or treated cellulose media typical of most replacement fuel filter elements. |
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100% "Marine Tuff" Multi-Stage fuel filtration with new SEAMAX designed Filter Heads, premium Fleetguard Filters, and "Drag Pointer" vacuum gages - With rated flows ratings to 100 GPH + with a minimum of restriction along w/ superior filtration and capacity, Multi-Stage Fuel Filtration has been proven in the toughest marine applications for over 20 years |
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Note: As I see it, all filtration before the engines "last chance" fuel filter is "primary" regardless of what you have in place |
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Simple and effective Multi-Stage Fuel Filter System. No messy & leaky bowls to deal with...
Excellent choice for 90% of all vessels |
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So what is "Multi-Stage filtration??
To me, proper fuel filtration for the type of marine vessels generally discussed in the forums at http://boatdiesel.com/ , all comes down to using a simple multi-stage filtration set-up (a minimum of 3 distinct stages/components) starting with largest practical and effective mechanical spin-on filter with around a 20-30 micron rating. This is your PRIMARY fuel filter (part of the entire "primary system" which is before your engine) and we call them "bulk separators" or "mud filters". In actuality, the first part of this primary line of defense can not only remove most of the mud and crud, algae and diesel fines, and extend filter maintenance many times, it can also remove copious amounts of water, but this will depend upon the type of primary filter you use and HOW YOU maintain it. And BTW, a Racor 900 or 1000 w/ a 30 mic element could also qualify as a "bulk separator" in my book, although I consider its proper long term maintenance is rather messy and very time consuming. |
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Basic Filter System Dimensions |
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Our preference for a proven Primary or Bulk Separator fuel filter?? In 95% of our work, the Fleetguard "spin-on" FF5013 is the ticket as it offers a 20 mic BETA rating, a flow rate of 100 GPH clean ½" Hg pressure drop, has a built-in water drain, has no "plastic" bowls to leak or discolor, and has proven itself to do the job. For super high capacity, we use the Fleetguard FS 1218 - About a 250 GPH flow rate, has a "crud capacity" of about 7 times that of a Racor 1000, and has all the best needed features for use as a high capacity Primary bulk separator. |
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Major YUK |
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Our second stage of the "Multi-Stage" fuel filter system |
After this primary line of defense comes your main fuel water separator, your Racor 900 or 1000 ( if you feel the need to have "Racor" on your boat) , or other type of quality fuel water separator. We prefer a Fleetguard FS19596, FS 1000, or FS1015 - listed in order of overall capacity and filtering quality - that has the largest capacity practical, using the most modern 7-10 mic media specifically developed for water separation. Notice I didn't mention the Racor FG 500 as I consider it too small (capacity wise) for anything over about 75 HP. What you choose here is usually governed by what the builder or past owner installed. And again, CAPACITY is the main key, as all of the issues that I have seen over years with problems in the fuel system and/or failed fuel components, is more or less related to the capacity, along w/ system component design and/or maintenance of this filter , and not the chosen micron size of the element, be it 2, 10, or 30 micron.
Our current choice for a properly designed and proven system is to use a Fleetguard FS1000 for the second part of the Multi-Stage system. The FS1000 Fuel/Water Separator was designed specifically to combat wear and corrosion in Electronic Injection Engines "EUI" technology. The FS1000 contains high performance synthetic media, "Stratapore" developed and made exclusively by Fleetguard, consisting of five bonded layers of multi-stage media. These are one layer of cellulose, three layers of melt-blown polyester and an additional protective layer. By itself, the FS1000 achieves performance previously obtained only with primary/secondary filter systems. |
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Racor 1000 w/ HD FS1218 Fleetguard primary bulk separator - Good for 700 hp |
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Upgrades for new Common Rail Fuel Injection & Problem Fuel Systems |
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Earlier, I mentioned "Common Rail" fuel systems, so I'd like to point out some issues that will now become important for all to understand.. First is that this fuel delivery design is now being used in many production hi-performance diesels for both on and off highway use. The design and idea has been around for decades, but it's use and current development has taken a major leap in the last year or so. With COMMON RAIL fuel pressures going well above 20,000 PSI from the pump to the "common rail" and all the way to the injector itself, a small amount of contamination, or especially water, that makes it to the pump and/or the injector will take on a whole new meaning. |
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Multi-Stage Common Rail Fuel Injection protection - FF 5013 and FS 19596 with WIF Sensor |
Complete On-engine Multi-Stage system with WIF Sensor and 2 mic "Last Chance" filter-required for Common Rail Fuel Injection specs - We prefer to call your "on-engine" factory supplied fuel filter as a "Last Chance" filter, as that's what it really is !! |
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In the past, many injection pumps have survived a teaspoon of water over an hour or so of operation, and still continue to march (although they may not be 100%). An injector may or may not have survived this water (usually not) , but typically, only a tip would go with no or minimum of damage to the engine and/or your pocket book. Let that teaspoon of water (or even 1/10 of a teaspoon) or the smallest amount of contamination get to the new common rail pumps, and it will most likely be an instantaneous major mechanical component failure ( your $2000+ fuel pump), along with a good chance of having an injector stick open that instantly starts dumping vast volumes of fuel to the cylinder or cylinders. This leads to everything from a major fuel / engine overload , scuffing cylinders, cracked/melted pistons, etc, all happening in just a few seconds. You could think of it as a serious engine run-away. Talk about why fuel filtration needs to be reevaluated with this new technology. And , that's why re-education is needed and why you'll will find that all companies that use common rail are requiring new and very strict filtration criteria.
One way Cummins has addressed these new filtration requirements is by requiring a WIF sensor "WATER IN FUEL" (two supplied per engine), that MUST be installed in the primary fuel filter (s) or "primary system" of the vessel for each engine. Besides that, they require a 10 MIC (minimum) primary filtration (meaning that you must use a 10 mic filter BEFORE the engine and this filter MUST meet certain minimum requirements: |
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Primary Fuel Water Separator Specifications |
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10 micron filter rating. |
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Separator must have a 36 gram minimum capacity per SAE J1905. |
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98.7% efficiency using ISO A2 test dust per SAE J1985 test methods. |
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Filter must remove 95% (or more) coarse water droplets over the life of the filter, per SAE1488. |
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BTW, these are the MINMUM requirements - Ask yourself, is that what you really want??
And, the new requirement for "last chance" fuel filtration on the engine is now 2 mic and this filter must also meet very strict requirements. Currently, Cummins is using a Fleetguard FF 5488 on all of the QSB's, QSC's and QSL's as the on-engine final fuel filter. A quick check w/ Fleetguard yielded this info: 2 mic Stratapore high performance media w/ 19 grams of dirt holding capacity, .95" Hg pressure drop/100 GPM clean w/ a 203PSI burst pressure rating. In case you don't know much about filters, that's a "filter" that doesn't let much past it, but then again, it needs to be supplied w/ a specific quality of pre-filtered fuel. In fact, and this point must be understood. These systems are so particular as to fuel quality, you must NEVER pre-fill these filters before installation. You must let the pre-filtered fuel from your off-engine fuel system do that for you thru the priming mechanism built in the engine.
So, where does all this leave us at this point?? Will this scare away many from this technology because these new engines are so particular as to fuel quality? It may, in some cases, because many out there are perfectly happy with their current era of engines, and "new" stuff is just too scary or expensive to deal with. But for anyone buying new engines, they need to be aware of these upgraded requirements and have a thorough understanding of what needs to be accomplished with fuel filtration.
And just like before, these requirements are a minimum to get by (typical boat builders usually supply the "minimum" in order to just meet requirements). The basics are easily met and can easily be engineered into a new boat or repower, but to add that extra level of security, extra measures need to be taken so there is plenty of room for error ( like getting a lousy tank of fuel, or having water drip thru a deck fill or down a fuel tank vent) and still not have any problems.
Another filter we are using as the primary bulk separator, are elements specifically designed for water absorption. "Cimtek" http://www.cim-tek.com/index.asp have developed filtration products specifically for problem systems and where extra protection may be needed.
Good technology, good reading on their site, and they also private label their filters for many large companies including Parker (Racor). That speaks volumes to me. We will typically add a third filter to the primary or Multi-Stage system using a water absorbing bulk separator if some has large amounts of water in his tanks and needs extra protection. |
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Basic Common Rail Fuel Multi-Stage system with WIF sensor - 100% Cummins, 100% simple, and 100% effective |
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Water Absorbing Filter Media |
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More reading and thoughts about modern fuel filtration |
"Microns" or Micron Ratings:
Now this is a term that carries some serious weight when selecting a fuel filter. Seems that average Joe is more impressed by the smaller the number, than the method used to measure or give the filter this "rating', the quality and type of media used within the filter, and the capacity of the fuel filter( dirt/water holding capacity).
Hmmm, rated 60 GPH with a 2 mic element-sounds way overkill to me considering my engine only has 300 HP and burns 16 GPH at WOT. This is where Joe has missed the big picture.
The "micron rating" of fuel filters is a very simple way of allowing someone to select just one of the requirements for filtration. Our experience with marine fuel systems has proven to us that the nominal micron rating is not the best way of choosing correct filtration. Micron rating should only be used to categorize the media since the most fuel filter ratings were developed based on single-pass efficiency tests using uniform spherical particles as a system contaminant. In real life, diesel fuel contains contaminants of various sizes ranging from sub micron to 100's of microns in size.
Keep this very important point in mind when you only think "micron rating" when choosing a filter - NEVER will you find a fuel filter with a rating of 10 microns, 2 microns, etc., that will stop 100% of the particles larger that this nominal rating. NEVER... What you will find with a quality filter is:
1) Beta Ratio micron rating
2) Fuel flow vs. pressure drop rating when clean
3) Dirt holding capacity vs fuel flow-pressure drop
4) "Free" and "Emulsified" water separation ratings
5) Ratings / specifications from SAE, ISO and other world recognized organizations
6) Other important parameters concerning collapse and pressure ratings, etc., that were developed in conjunction with a specific requirement from an engine manufacturer.
Keep in mind that Cummins, specifically, does not recognize micron ratings as significant and specifically recommends the use of "Beta ratio" in selecting a filter to meet system requirements. I am certain many engine manufactures are of the same as to their requirements.
More help follows if you want to get real serious about fuel filtrations basics:
A "NO BS" guide to filtration and what it all about - Trust me, no "gizmos" here!! http://wfc2.xapnet.com/filtration_basics/index.php
FRAM ( those "auto guys") also makes it easy to understand some basics about microns and "BETA" test methods http://www.fram.com/pdf/FluidFilterRating.pdf |
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Can you have "Too Much" filtration ?? |
I am not one to argue another author's ideas on fuel filtration when I think someone is suggesting (in so many words) that fuel that is cleaner, is better. So, I 100% agree it would be very difficult to say that "too much" fuel filtration is possible with the fuel injection equipment used w/ these 60-80HP per liter diesels today, so having fuel "too clean" may not applicable anymore. But, of course there are practical limits as to a filtering system that filters to well beyond needed cleanliness, and I will suggest that maybe something along the lines of practicality might be missing in many ideas written on the subject.
This is what should be conveyed and understood about "too clean"... |
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Triple Multi-Stage for problem fuel tanks - (Left) QSL's in a small "crew boat" with problem fuel tanks - No chances taken here as we have a "water absorbing" media filter in the middle and a FS19596 with a WIF Sensor as our polisher/final stage - never too much! |
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Actually, filtering down to a nominal 2 mic level probably could have some quantifiable benefits ( injector seat & injection plunger/cam wear), even for and an engine that does not require that level of filtration. But this is not the reason I sell replacement injection pumps a couple of times a year and rebuilt injectors about 10 times a year. It's because of water contamination, and the fact that the operator only relied on his 1st line of defense (typically a "RACOR") and the marketing hype around it that led to complacency regarding fuel quality... So, I'm not going to argue about whether filtering below manufacturers' specs has a benefit - what I'll argue is the way most people filter fuel. And, that typically is that the vessel and / or operator is relying on a single filter to remove water and contaminants before he sends that "filtered" fuel to his on-engine" last chance fuel filter - This is a major mistake in judgment as to think that the last chance filter will save him. We hope to convince our customers that a well designed fuel system will deliver fuel to the engine, and to it's "on-engine fuel filter", that is all ready clean enough that he is not relying on this "last chance" filter to save him.
My thoughts, experience, and reasoning will never change about using multi-stage "primary filtration" and making sure you have the filtering capacity to get you through a lousy tank of fuel, or maybe two. With the advent of "common rail" fuel injection, just the slightest amount of water that makes it to the pump and/or injector will now have catastrophic consequences for not only your fuel system components, but could also take-out the engine.
Some RACOR Thoughts
A Racor 1000 can have very acceptable capacity when used w/ a 300-600 HP engine in typical recreational service. Use that same filter on a 200-400 HP diesel in an application that runs 2000-5000 hours per year, and in many/most cases if this unit used as the only filter before the engine, this widely used filter has unacceptable life between maintenance intervals. My point here is that designed flow rate of a filter should not be the only reason for selecting filter size but rather needs to be chosen based upon the application and vessel current use, and past fuel problem history (if any) of the vessel.
As many operators will confirm from personal experience, servicing a "Racor" can be a challenge if you want to try and keep the bowl clear and clean. Lots of parts, seals and just a plain hassle and extremely messy to deal with. But, get it clean once, install a bulk separator in front of it, and you'll see a noticeable change in the maintenance of the Racor over the next few years, along w/ giving you that added layer of protection. Also, more times than not, I have seen the bowl on a Racor so dirty that its effective use as a "visual" has become totally worthless. My preference and experience is not to rely on a "visual" at all, but to drain a sample of fuel before you use your vessel. Maybe that reasoning comes from my training as a military pilot way back when, but for sure its merit cannot be questioned. Also, adding a WIF sensor is easy on the Racors and a few other types of filters. The factory Cummins VDO panels and harnesses are all ready set up with WIF circuitry/alarms, so if water has been an issue, you really do not have an excuse not to hook it up. |
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Practical Fuel Filtration to 2 MIC |
Now that you have convinced yourself that you want that 2 mic filtration regardless of the engines requirements (I have no issue with that), but let's do it in a practical fashion.
The last thing we want is to have that 2 mic filter to be hit with the crud coming from the tank. Filtering to 2 mic BEFORE the fuel gets to the engine may become a maintenance nightmare unless you have extremely large capacity in both unrestricted flow and element size, but would still have NO PRACTICAL sense to it if using only a Racor 1000 w/ a 2 mic element. It may be fine for a few hours of running ( a few to me is at least 50) , but most likely will lead to fuel restriction problems quickly. Running a pair of these (switch-able parallel), will certainly extend the time between element changes, but seems to be another impractical solution... The last chance filter on your typical engine is in the 5-10 mic range, and should be fed with clean fuel-no argument as we believe that filter should stay clean for at least 500 hours or more.
But again, if you want more practical assurance of delivering clean fuel to your engine (which is a GOOD thing) , filter before your Racor, or add another in series, but filter your fuel in micron stages (60 / 30 / 20 / 15 /10 / 5 / 2 mics ) as this is how practical filtering is done in all industries or applications. And, as with the addition of any more filtration, your choice of plumbing, and capacity and pressure drop across the total system when clean, needs to be accounted for. Even my own "basic" sizes for fuel suction hoses for applications that only needed ½" in the past, are now being re-evaluated as many may now need 5/8" id (or larger) hose because of stricter fuel filter requirements needed by newer engines.
Properly set-up, it is very easy to install a practical 3 or 4 stage fuel filter system that has a pressure drop across the entire set of filters of less than 3" HG at a flow of 75GPH or higher, and one that gives extended service intervals. But do this in reverse order with smaller sized filters in front, you'll now have a system that will "clog" well before it should and will be much more expensive and time consuming to maintain or diagnose. A vacuum gage installed just after the last suction side filter will tell you when to change filters, but will have "less meaning" unless the filtering is done in correct order, from large to small. And, if your vessel use really dictates even more filtering capacity, then double up by paralleling two identical systems or by paralleling the primary - "primaries" only.
What I'm trying to get across is PRACTICAL fuel filtration - "filtering done in stages" - that has been proven to be effective long before I came along, but has been reinforced over the years from my own experience. My main customers are fuel burners of well over 5,000 gallons per year per engine, with some approaching 40,000+ gallons per year, so this is where I come from, NOT from something "I read"...
For a typical 8-12 L marine engine w/ flow rates of around 75 GPH and someone who wants to use a simple and very effective multi-state fuel system or a "primary fuel system"* before feeding fuel to his engine last chance fuel filter, using the Fleetguard FF5013 in combination with a FS 1000 is a proven and very effective system. For a simple upgrade to this, using the new FS 19596 with a built-in WIF sensor ( this is a new filter that fits/replaces where the FS1000 does, has more dirt holding capacity, and is a 7-8 mic hi-performance unit rated at 90GPH w/ a minimum pressure drop), he can't go wrong. This combo is miles ahead in capacity, quality, safety of delivering clean fuel, and ease of use, compared to a Racor 1000. |
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Vacuum Gages and Fuel System Restriction |
Installing a vacuum gage in your fuel delivery system is a worth while option and will pay for itself quickly when its function is understood by the boat operator.
Restriction or "Fuel Pressure Drop" across a filter is a function of fuel flow vs. restriction or "clogging" of the filter. A well designed fuel filter system, which includes all the types of fittings, hoses, valves, and "other things" incorporated into the finished system, should start out CLEAN under 3" of Hg restriction, when measured in-between the lift pump and the last "off engine filter". We typically mount the gage on or after the last filter in the primary Multi-Stage system because of convenience, and the fact that we do not consider the fuel line and fittings (if properly sized) between the last filter and the lift pump to be of any consequence in the overall restriction of the system.
My field work over the past 20 years has shown that "most" diesels with properly operating lift pumps and fuel systems can tolerate about 10"-15" of mercury (Hg) restriction before starving for fuel... Again, always put your vacuum gauge after your "off engine" fuel filters, but before any pumps. And in actual operation, you will find that a good Multi-Stage system will clog 2-3 primaries (FF5013) before the FS 1000 needs replacing - The vacuum gage will tell to that as that is what multi-stage is all about. |
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Multi Stage System - Parallel set-up for twin Main engines w/ single for twin 20 Kw aux engines |
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Tips for Your Selection of a Fuel Filter System |
In all cases, regardless of how one decides to set up fuel filtration system, give these ideas / fuel system tips some thought, or keep them for future reference... And if someone has a few ideas to add, please don't be shy as this is one of the main premises behind these forums "sharing information and ideas so all can benefit".
A few pointers below to help YOU make the right decisions....
1) It's always best to either draw your fuel from the bottom of the tank (you want the crap in your filters and not sitting in the bottom waiting to get stirred up in the first bad weather), OR have a drainable fuel tank sump, OR BOTH.
2) Be sure the fuel lines, valves and fittings that feed your filters do not restrict the flow or allow air to enter the system. Choosing the next size of filter in capacity ratings will assure you of a longer time between clogging.
3) A vacuum gage installed just before a fuel lift pump will more that pay for itself if installed correctly and its operation is understood by the operator. The use of a vacuum gage adds "science" as to when to change your filters. |
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Easy View Vacuum Gages |
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4) An in-line sight glass or clear piece of vinyl hose (temporary) installed in the fuel line is one of the best tools for addressing fuel / air leaks in a fuel system when troubleshooting .
5) Always be sure the filters you choose to use are sized in stages with the largest capacity and nominal mic rating closer to the fuel tank. "Multi-Stage", remember??
6) Be sure your "return fuel system" cannot be shut off when switching tanks or at any time during engine operation.
7) If the engine fuel system design allows the use of a submerged return line, consider this as a worthwhile addition to the fuel system. But, also read your engine installation requirements as not all systems recommend this, although MOST DO.
8) Fuel transfer: With multiple tanks and the need to transfer fuel with an electric pump, putting an old fashion type spring wound timer w/ normally open electrical contacts ( available thru many home improvement stores and industrial supplies) will save you from the many embarrassments that typically occur by pumping fuel into the bilge or overboard due to overfilling. I rarely recommend using return fuel for fuel transfer because of typical flow rates above 60 GPH in many cases, it is easy to "forget" about the valve you messed with a hour ago. We prefer using a 12 VDC electric pump with flows around 30-50 GPH with a fuel filter on the suction side of the pump (FF5013), w/ 60 minute timer. Not only will you not forget, you will be "polishing" your fuel in the best way - with the boat "rocking and rolling". Need 50 gallons moved from port to starboard?? Just the right twist and your done !!
9) If you really want to know what type of ugly stuff is in your fuel tank and how good your filters are really working, cut open your "on-engine" spin-on and take a look. This is the one method that will let an operator really find out what is getting thru to his last chance filter on the engine. Cutting open filter in your Primary system, will tell you what's really in the fuel tank.
10) If you have "Racor Phobia", but tired of the mess having to take apart your Racor Bowl to clean it out, put a bulk separator spin-on in front of it. You'll be amazed a year down the road at the difference.
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Multi-Stage with Racor's and fuel transfer polishing system |
Simple and very effective upgrade for Racor's - Adding a bulk separator as the primary |
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11) Be sure none of your fuel tank vent lines contain a "low spot" - you want them to drain completely when the boat is static or in motion. If they can run forward and rise at the same time, this is always a better choice for routing. With large wing tanks, it is usually best to vent on the inside top and fwd edge of each tank. This allows the tanks to vent better if the boat starts to heel during filling.
12) A properly installed sight gage on your fuel tanks is the best assurance of knowing how much fuel you really have.
13) When building / designing a fuel system w/ many pipe thread type fittings, manifolds, etc. consider the use of a 100% solids epoxy for the "pipe dope". Many installations cannot tolerate even the slightest "sweat" of diesel on a fitting. We started this practice about 15 years ago, and we never get a "call back"... Grey "Marine Tex" and some Simpson (ET-22) products do a great job and will never let you down, besides being easy to use and clean up. |
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"No Diesel Sweat" - Fuel Manifold with 100% epoxied fittings / threads |
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In closing, multi-step "Multi-Stage" filtration is the most effective and simple way to protect modern diesels from the contaminants found in fuel systems. To quote "Alaska Diesel," (you know, those Lugger and Northern Light guys,) "Forcing fuel to go through even three separate, progressively finer filters is cheap insurance.".... |
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Multi-Stage & John Deere / Lugger - Good Friends!! |
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Tony Athens | September 1st, 2007
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Back in the 1970's I became heavily involved in the mechanics of boats and before I knew it they became my passion. I have been lucky to have gained over 25 years of experience and 10's of thousands of engine operational hours (300+ diesel engine installs) and have learned (sometimes the hard way) what it takes to make a reliable engine / power train system, and all that that incorporates. The Marine Exhaust System is a major part of this. |
My hopes are that the information in this article will shed some new light on the understanding (and misunderstanding) of one of the most important aspects of a successful boating experience: The Marine Exhaust System.
An important goal here is to remove some of the mystery surrounding much of the misguided and ill conceived "couch engineering" designs that have been imbedded in the boating industry for far too long. Some common sense is the first part that is needed to design a safe and reliable exhaust set up. And, the key word here is "GRAVITY." Just putting some thought into the general placement of your exhaust system, and with the knowledge that I hope you glean from this article, should help solve many, many horror scenarios down the road. Also remember this (something you can take to the bank), doing it right the first time will leave your wallet much more in tact in the years that follow. |
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It has been a few years since I posted some thoughts, pictures and politics on Marine Exhaust Systems, so it is time to update. And, since exhaust system design, fabrication, and installation have become a large part of our business, the time is here to share some of what we have learned over the past two decades in this ever changing business. |
First and Foremost -
The two most basic issues that need to be understood and accomplished: |
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A safe system for both the boat, on board personnel and the engine, it needs to be long lived & must meet manufacturers' requirements as to back pressure and water entry. |
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The exhaust design and/or system must fit the boat and work in such a way that water will never flood the engine, even if something fails, and the system needs to look "politically correct". |
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To this very day, much of our work still involves replacing, rebuilding, or repairing engines solely because of a poorly designed and/or fabricated wet exhaust system that allowed salt water into an engine's internal workings. Seems the most basic of all natural forces in our lives, "GRAVITY," was "left out" of the design process, and then, mixing that with couch engineering and "back yard designers," you now have a recipe for disaster someplace down the road, sometimes very soon after you purchase a new boat. |
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The components of a basic exhaust riser: Adjustable & weldable turbo flange, elbows as needed, straight pipe for additional rise, and a properly designed exhaust mixer pointed in the right direction to eliminate unnecessary "wet bends". |
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Let's start our main discussions with exhaust sizes (NOT overall design, as we must first figure out what is required to meet engine requirements), dissect them a touch, and then decide what is needed and what will work. You must also understand that when we talk "marine exhaust" we are usually talking a "wet" system, but also realize that inside this "wet system" we have two distinct parts. In most exhaust systems that are in the type of boats discussed in these forums (150-800 HP diesel engines), there are TWO distinct parts of the exhaust system/piping. The DRY part and the WET part. Even on the factory supplied 90 degree "wet elbow," these two sections exist, though many people don't realize it. |
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Cummins QSB 380 in a 27 ft Farallon - 4" dry to 5" mixer. Under 25" H2O at WOT. |
Port and starboard Cummins risers - 4" dry to 5" mixers - Very simple and basic in construction. |
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The inner pipe of this "wet elbow" is actually/usually a 90-degree dry bend, or section, surrounded by raw water to keep the surface cool. At the end of this "wet" elbow, where the exhaust hose attaches, is where the water is introduced (hence the term "mixing elbow") and the exhaust NOW becomes wet. Inside this elbow is a smaller diameter (typically around 2 ½ - 6" ID) which is the dry side, and where the hose attaches (it expands to (or is surrounded by) 4-10" tubing/OD piping, depending on the engine size, etc.) |
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EXHAUST SIZE can be determined by a few rules, but all really come down to two things: |
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#1 - Meeting the engine requirements as to total restriction (back pressure). |
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#2 - Designing a system that will FIT inside the boat's constraints. |
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Most Important Point to Understand - Very simple, if you can't meet Rule #1 and Rule #2, then nothing else matters and the exhaust is the WRONG SIZE. One, it won't meet engine specifications / requirements, and two, it won't fit within the constraints of the boat.
As to meeting engine/manufacturers' requirements regarding "back pressure," this is where it is so vital to select the correct sizes of piping & mufflers, design the actual layout or flow path, and then put it all together so exhaust flow is not allowed to build up over this maximum pressure limit assuring safety in all aspects related to the installation.
Exhaust back pressure measurements are a very low number, something like what it takes to blow up a balloon. The pressure is usually measured in units of Water Column Height or Mercury (Hg). Typical maximum limits are from 1.5" Hg to 3" Hg or 20" to 40" of water (right around 1 PSI), depending upon the manufacturer. John Deere, Lugger and Detroit seem to want back pressure lower (about 30" water max) than Cummins or Yanmar (40" to 50" water), and this makes it even tougher to meet the requirements and build a system that will fit. A new specification for exhaust back pressure limit from Cummins for the QSB was just released that will easily allow a well designed 5" WET system to meet back pressure requirements on the QSB 380 and possibly even the newest 480 version if a well thought out design is used. Cummins now allows 5" Hg (about 2.45 PSI-68" of water column) on all the QSB's. This is a very friendly spec and can make for a much easier and less expensive exhaust system installation. |
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370 Cummins, with V-Drive with high mount turbo 3" dry to 5" mixer - One 90 degree wet bend - Under 10" H2O at WOT - Very simple and safe arrangement!! |
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Yanmar 6LYA custom riser - 4" dry to 5" wet mixer to 6" transom exhaust - Under 35" H2O at WOT. Notice 160 degree F temperature alarm on "cold part" of mixer. |
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But, back to sizing. Exhaust flow is determined from the amount of HP the engine makes and the more HP, the more exhaust flow; therefore it will take larger piping and/or less bends, shorter lengths etc., to meet back pressure requirements. Also, a very simple to understand concept (even though most installers seem to forget) is the "bend" equation part of planning an exhaust. Figure a smooth radius 90 degree bend is equal to about 6-10 FT of DRY piping and 15 FT of wet piping. Another good rule of thumb to remember is for every 100 PRODUCED horsepower, the engine makes about 200 CFM of exhaust gases, but this does not include the water and / or steam that becomes part of the mix when water is introduced. That's why dry piping can be smaller than wet piping, WATER and steam add to the total flow in a substantial manner; therefore once water is introduced, the piping MUST BE LARGER.
Past experience as to what size will work and meet requirements is always a plus when in the initial planning. But not all are so lucky, so they turn to the engine specs or installation guide and see what is "recommended," and/or they use the factory supplied wet elbow size to go by. In some cases this is fine and gets you by with the least amount of cost and effort. In most cases, the hose size that fits the factory elbows will work in 90% or more of the applications out there.
Below are some notes on 3 most common WET exhaust sizes that have shown to meet all restriction requirements for Cummins engines over the last 20 years and are based upon well over 300 Installation Reviews and exhaust tests. Keep in mind that the dry section and wet section are different and must be treated so. Also take into consideration the type of muffler, the overall length of the system, the amount of both dry and wet bends, the amount of water that you inject into the system (some of it, if not all of it), the angle of the discharge AFTER you inject water and how the system exits the vessel. All of these affect the total system back pressure. I am using Cummins engines as that is what most of my experience is with and I am using 3" Hg or 41" of water column as the maximum back pressure limit: |
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Learn to understand the nomenclature difference between "pipe," "tube" and "hose" dimensions.
For this discussion, pipe size is always shown as a nominal size in SCH 10 wall ( .120"-ish) - I.E.
2.5" = 2 7/8" OD,
3" = 3.5" OD,
4" = 4.5" OD,
6" = 6 5/8" OD, etc.
"Wet" size is always the actual ID of the exhaust hose. Tube is always the actual OD of the tube (pipe) and is usually about 1/8" wall meaning a 5" WET tube or FRP (fiberglass) exhaust tube or pipe has approx a 4 ¾" ID.
Exhaust hose (any hose for that matter) is always sized as an ID measurement and always is sized to FIT OVER a tube OD dimension or pipe outer diameter measurement. |
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4" Tube, 4" pipe size ( 4.5" OD) & 5" WET SYSTEMS - 6BT 210, early 6BTA's - ( 200-250 HP) Factory recommendation is 5" WET (Yanmar 6YLA too), or most any diesel in between 180 and 250 HP.
Experience has shown that 2.5" pipe (2.875 OD) for a short length or one "90," OR 3" pipe size ( 2-3 90's) for the dry section, and 4" tube to 4" pipe for the wet section and wet muffler is usually fine. This would also apply to a 4LHA 240 Yanmar and 6LPA 315.
6" WET SYSTEMS - 6BTA's - 300 ~ 370 Diamonds and QSB's thru 480's, QSC's , QSL's ( 300-500 HP) - Factory recommendation is 6" wet. |
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5" to 6" transition |
Typical 6" 8" wet FRP "low restriction" transition wet elbows |
Heavy Wall Construction to prevent factory type "crush" failures |
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Well, this is where we have some "fudge factor" if you want to design it right and make it "fit" the boat. Going from a 5" wet to a 6" wet ( typically in 300-450+ HP engines ) is HUGE and opens many install capabilities. We like 6" mufflers and piping from the typical engine room bulkhead aft to the exit near or at the stern. But we like to do our engine risers/custom elbows and wet mixers in 4" pipe for the dry section and 5" WET outlets where space is an issue. Using a properly designed dry riser w/ a 5" mixing elbow, and then transitioning to 6" at the engine room bulkhead, saves valuable space in smaller engine rooms, saves money for the customer, and is just about always easier and a better overall and "politically cleaner" install. The transition from 5" to 6" wet is always easy as 5" to 6" FRP tube is an easy make for a custom elbow of any degree at 45 or less. If a highly restrictive muffler is used, or the available space allows the use of 6" close to the engine, then a 6" mixer might be the best choice. |
Transition from 5" to 6" wet
6" tube to mufflers to stern
5" wet mixer
4" pipe size (4.5" OD) dry riser
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4" Dry riser, 5" WET mixer to 6" wet FRP pipe transition |
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8" WET SYSTEMS - Some "C" & QSC installs, QSM's-400++ to 800-ish HP-Cummins has "recommended" both 6" and 8" and seems wishy-washy on this.
Well, I have yet to see a C, QSC, QSM, or any Cummins (or other make) engine UNDER 500 HP need an 8" wet exhaust system to meet specs. But, I continue to see this as a RECOMMENDATION for the exhaust size in many cases. I guess if you have the room, the budget, and have an extraordinary amount of bends and/or an overly restrictive muffler, then maybe you should go for it. But from a vast amount of experience, we always stay with 6" max if under 500 HP.
When we get up into the 500 - 800 HP-ish HP range, this is when we need to think about some, or all, of our WET side of the system being 8". Since most of my work and the discussions on this site center around repowers of sportfishing boats like Bertrams, Vikings, Hatteras, etc, let's confine the 8" to this general style of boat in the 40-60 ft length range. And, with so many older Detroit powered boats/owners still out there that are now seriously looking at repowers, and most of these having 8-71's , 6-92's, 8-92's, etc., this is now even more important to understand.
Usually, these boats have 8" or even 10" WET systems aft of the engine room. This is typically where the mufflers are located too. If all is good aft of the engine room - all piping, mufflers, outlets and hoses - (it is usually not), then this is a good size to start with for adapting to the newer 4-stroke engine. If some or most of this piping needs to be replaced because of age, it's usually easier just to stay with the same size for the section aft of the engine room. If you'd like to size down for space or cost reasons, then a good look at the overall system and engine requirements will be needed.
Let's look at a new QSM at 670 HP as to what will easily meet the spec. The factory supplies an 8" fabricated wet elbow or mixer and IMO is of questionable use or quality. Yes, they do work in many applications when used correctly, but also seem to be subject to both internal and external leaks before their time because of the many welds and thin wall construction. Even worse, though, are the "installers" who re-weld or bolt these units in a dangerous "up" orientation in order to build a cheap "Mickey Mouse" type riser. I not only see this with the QSM's but also in many other installs using the factory 5" and 6" "factory" wet elbows. |
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Cummins 300B's with reorientated factory elbows - 700 hours over 5 years and water was leaking into the turbo - Luckily it was caught before an expensive disaster struck. |
Cummins QSM 11 with "reorientated" factory wet elbows - This owner was told at sea trial that they would fail internally, he said he would fix them. Never did.... |
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For those who cannot grasp what the issue is here, a simple explanation - This is a double walled 90 degree wet elbow that was never designed to "hold water" in this orientation but, rather, be mounted horizontally so as to exit downhill and self drain. When installed like this, the sea water that will eventually corrode thru the elbow will now go down the pipe into the turbo or worse. I hope you do not recognize this type of system on your boat!
Now, back to 8" - This is what we have found with engines in the 600-700 HP range as to designing a wet exhaust system and working around the existing 8" - 10" piping or "book" recommendations. We typically use 4" dry piping from the engine up to a well designed 6" wet mixer. This usually includes 3 to 4 pieces of 4" pipe size "weld" 90 degree dry elbows and then a double walled wet mixer of our design orientated on the downhill side of the system. The mixer is always pointed to a spot on the vessel so we DO NOT have to incorporate any WET bends / "90's", etc., BEFORE the transition to 8" (or 10") from the engine room aft.
With good design and thought, along with some first class fabrication, meeting exhaust restriction requirements can easily be done with a mix of both 4" dry, 6" and 8" wet which will make for a much cleaner install while making the engine room more user friendly as to maintenance, etc.
To recap, exhaust size is something that can be adjusted to not only meet requirements for the engine, but also fit the vessel's constraints. When sizing the system to meet acceptable restriction requirements in order to protect the engine from excessive back pressure, keep bends to a minimum, especially "wet" 90 degree bends. With some planning, most exhaust routing designs can eliminate a one or two 90 degree bends by building a custom riser/mixer and make for a less restrictive, less cumbersome and safer exhaust system.
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In closing, please understand that with some good engineering and thought, a well designed exhaust system can make a big difference in the layout of the engine room and offer a superior design as to safety and functionality. The idea that rarely a month goes by without our shop seeing a disaster from water ruining an engine from a "factory" type exhaust system or from an OEM builder with his head between his legs still befuddles me. To this day I see drawings from architects who have no clue. The drawing below is from a boat being built that is just such - All that height in the engine room and the architect has the system riser backwards - Just ask yourself what would happen while cranking the engine when out of fuel. And just as bad is that he got paid to design it this way. Sad, very sad....... |
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Total 100% couch engineering, but the guy does do nice drawings. |
Marine Exhaust systems are one of the more important construction features on a vessel. Done wrong they are not only a safety issue for the passengers and the vessel, they can also lead to premature engine failure and / or indirectly cause poor maintenance to be performed on a vessel because of lack of design thought in the engine room. So many times when the exhaust design is an "afterthought," normal or routine maintenance is close to impossible.
If you give this some thought in the future, maybe this will help you in your next repower or new boat design - The energy that a typical 400 Hp diesel puts into the propeller is matched close to 100% by the energy that goes out the exhaust system. So if you think your power train needs to be well designed, don't cut any corners on the exhaust design - It needs to be just as tough and built with the same degree of design to handle that kind of energy.
Hopefully the pictures and design ideas incorporated here will help remove some of the mystery in exhaust design that seems to elude much of the industry. I fully understand that a buyer of a new boat does not have much input as to exhaust design when purchasing a new or used vessel, but we hope the guidelines here help not only the buyer to understand what to look for in a boat, but also will prove to be beneficial to the builders in the design and planning phase of marine engine rooms.
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Tony Athens | October 1st, 2006
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Designing a marine exhaust system |
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Designing a marine exhaust system for a boat is something that apparently takes the back seat during the planning stages when doing a repower. In new boat construction, the design of many systems seems to center around the "cookie cutter" philosophy, as builders always seem to want to or work around a factory designed wet elbow system that is supposed to "fit all". Besides that, many new builders are more concerned about getting the engine below a low deck than worrying about the exhaust and exhaust outlet of the engine being close, at, or BELOW the water line. |
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QSC Starboard Cross-over riser - 4" dry to 6" wet mixer to 6" surge tube. |
Cummins 6CTA 8.3 with "twisted" dry riser -4 " dry to 6" wet - This design eliminated 3 wet 90's that the original system had. |
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Also, and another all too common error in exhaust design, is the use of an anti-siphon valve as a "fix-all" for an otherwise poor and sure to fail design. It's not that an anti-siphon valve is not needed in many applications, but "Average Joe" has no clue as to what they can do and more important, what they CANNOT do, and how small changes in the basic design of an anti-siphon valve can greatly enhance its effectiveness. More on "Anti-Siphon" valves and their shortcomings below.
The most BASIC of all supposedly understood but not followed diagrams of a marine exhaust layout is below. Why is it we continually see the LWL of a vessel within just a few inches of the exhaust spill-over point? Notice the word MINIMUM?? |
CARDINAL RULE #1 - Wet Exhaust Height Above LWL
REMEMBER this as the "SPILL-OVER" point |
The diagram above seems to elude new boat designers and "repower experts" in so many designs that have cost vessel owners millions of dollars over the years in ruined engines. Simply unbelievable to me that something as simple as building an exhaust with a minimum of 12" of safety margin height is not followed.
Moving on to the total design of the system is where most of the emphasis needs to be when repowering or building a boat. With "design" we mean the entire system from the engine exit point (the turbo outlet in most cases) all the way to where the exhaust leaves the boat. This includes the "size(s)" (just figured that one out), from the engine to the final exit, type of muffler, if any, type of material for both the dry and wet side of the system, and the general routing and actual installation of the system. It seems that many installers and builders plan this very important part of the vessel as an "afterthought" because many great engine rooms are built with no room remaining to build a safe and well planned exhaust system. |
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Starboard QSM riser - 4" dry to 6" wet. |
Cummins 330B / V-drive - Simple Riser points directly to stern exhaust exit. |
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Material choices when building exhaust systems can vary, but 25+ years of experience and 100's of exhaust systems under our belt in high hour commercial applications have shown us that 304L or 316L is good for all of the dry sections and shows no difference in lasting ability regardless of what "street talk" says. Using 316L for all wet sections is always best. Use 316L rod for all welding (304 or 316) and if the design uses any mild steel for the dry section, then use 309L for the mixed joints / weld area. TIG is the method of choice for all welding. For all custom FRP exhaust work, the of use resins that are Class 1 fire retardant isophthalic polyester resins are our choice and easy to source. Common industry names are Reichhold (DION) and McNichols and are used extensively thru the FRP structural pultrusion process and filament winding manufacturing industry. You may also find many of the more common iso-tooling resins meet these specs and are also an excellent choice to use, although some do not have the Class 1 rating. IMO, 99% of the time, Class 1 resins are not needed unless the spec calls for it.
Resin rich lay-ups are best with plenty of thickness ( ¼" to ½") in all joints building up with glass-strand mat with a layer or two stitched fabric in-between. We finish with iso-gel coat and surfacing agent when applicable / paint as to what looks right for the job - in all cases our work is always vastly more stout than "factory supplied" FRP parts, and we always put a 2" - 4" long tube doubler inside all tubes where the hose clamps go. This eliminates the tube crushing that factory pipes/ muffler spigots seem to be very susceptible to.
With sizing and basic construction covered, let's get into exhaust design, as this is the most abused and least understood phase of the overall system. "Gravity," I'll say it again, "G-R-A-V-I-T-Y," is the most important aspect of the design that needs to be addressed and how you can use that force to help you design a safe and effective exhaust system. Next is understanding and knowing where your waterline is in both static and all running conditions.
With those ideas fresh in your mind these are some pointers and concepts that you need to consider in the initial planning stages of the design layout: |
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1) Understand the difference between a "requirement" and a "recommendation" from the engine manufacturer regarding exhaust design. They may "require" a minimum specified exhaust height for safety, but "recommend" a particular size for the system based on past experience. Many times smaller exhaust sizes can be used to everyone's advantage and employing an experienced company w/ hands-on experience for this part of the vessel construction or repower is time and $$ well spent. |
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In the shop exhaust "mock-up". |
Measuring for a custom exhaust riser from drawings / dimensions supplied from owner 2000 miles away. |
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2) Always use gravity to your advantage. Water flows downhill so, if you have a system that holds water (water jacketed risers for instance) and this system fails internally (it's not IF it is going to fail, it's WHEN it will fail), where will the water go?? Into the turbo/exhaust manifold/cylinders?? Think about YOUR riser or elbow should it fail internally where you can not see it and what might happen. Remember, WET risers are an absolute no-no for any long term application unless they are "coolant cooled." Internal failure of "wet elbows" and custom water jacketed risers is an old and ongoing problem, regardless of material choice and/or other claimed construction features. (See Tip #7). |
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3) Always use all of the available height in the engine room for the riser (where needed and is practical) BEFORE turning over the top and injecting water; i.e. always inject the water on the downhill side, or down stream of the top of the riser. A wet exhaust system with a steep downward slope is always better and safer. The cheap way out, by using a factory supplied "cookie cutter" designed wet elbow, is not always a good or safe option. When thinking marine exhaust, remember "one size" DOES NOT FIT ALL. |
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4) Be sure that IF the option presents itself in the design of a wet exhaust system, allow for all of the water to drain itself from the exhaust when not running. Although this can't always be done, you can still build a safe system by utilizing other simple design ideas, custom mufflers, surge tubes, etc. An important point to remember, IF your muffler, etc., holds water in the static position, then the system is also holding water when lifting/pulling the boat at the yard. ALWAYS lift the bow first (noticeably bow high) and hold it there for a minute or so to let the water drain from the system. I have seen quite a few destroyed engines that had water slosh up into the cylinders from this exact scenario of water rolling back and forth or lifting the stern first when pulling a boat - Usually this is not discovered until launch time and by then the engine is toast. |
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5) When using a "lift muffler" design, remember that in most cases you can make the system "inherently safe" by being sure that the engine "spill-over" height is higher than the lift muffler spill over point. When the water injection is below the water line, you can also design an "active" anti-siphon valve that is much safer than the typical "auto-type valve" shown or used in most applications-(IMO, they are a poor design and should be avoided unless fully understood as to their shortcomings and checked for proper operation on a continuous basis ). |
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Some of the fallacies that still persist today are shown in the "copied" lift-muffler design below that is shown in current high dollar color catalogs touting their exhaust muffler products. Thinking that this is an applicable base type design for a lift muffler system is 100% hogwash and in many cases leads to ruining a perfectly good engine because of water rising within the system before the engine starts and after it is shut down. What they should be saying is to design a riser BEFORE the water injection to use all of the height available within the engine room, and to design an anti-siphon system that allows an active and "open" siphon break to be on the upward rise of the water injection system allowing water to flow over the side BEFORE the water flows into the lift muffler filling the system. |
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Again, another instance of 100% "couch engineering" from an engineer that has probably never done and/or seen an install of a marine engine at or below the waterline and only gives or sells his "expertise" based on theoretical circumstances on paper calculations. This kind of literature angers me as I know it's total garbage. However, I do admit that when this type of engineering is taken for "gospel," I make lots of $$ because it assures me of continuous new engines sales down the road. |
To exhaust elbow |
From heat exchanger
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Anti-siphon outlet / dump |
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Active "Anti-siphon" bypass/valve installed on the uphill side to overboard discharge. |
Active "Anti-siphon" bypass / valve installed on the uphill side to overboard discharge.
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The general layout of the "anti-siphon" valve. In reality, it's not a valve at all, but an active bypass that should be installed on the uphill water flow before it goes over the top, and discharged over the side above the waterline in a VISIBLE location. This allows cranking without flooding the lift muffler and adds an enormous layer of safety to the system.
6) Overall Exhaust design can usually be made better in many ways if you DO NOT use "cookie cutter" type exhaust components. Typically, many use factory 90 degree wet elbows, and an array of 45 and 90 degree bend hoses and clamps routing an exhaust. I guess most installers think of a marine exhaust system like copper plumbing in a house.
A simple change from a 90 degree angle bend to a 75 degree bend, an angled input to a muffler, or an added twist in a riser can make a world of difference in overall exhaust layout. In other words, don't just think "straight, 45 & 90" when designing an exhaust system. In the 100's of exhaust systems we have designed over the last 25+ years, I am sure that at least 50% of them had to have something custom done to a "factory muffler" in order to make the exhaust layout "fit" design criteria. |
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Yanmar 4LHA 230 - Modified 4" Muffler inlet - Eliminated (1) wet 45 and (1) wet 90. |
"Modifing a muffler like this will lower exhaust pressure, save valuable space and cleans up the total system." |
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An Interesting Note: I have tested the pressure drop of a typical 75 degree custom elbow from both 6" to 8" and 5" to 6". In both cases, at 430 HP on the 5-6" elbow, and at 660Hp on a 6" to 8" elbow, I never saw more than ¼" Hg delta. Going from smaller to larger allows a quick expansion and lowers pressure restriction overall even in relatively sharp wet bends. Less bend would even be better. |
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7) Never, never, never do you want a boat that has saltwater cooled wet risers or pipes unless they are installed in such a manner that when they leak they are downhill of the engine "spill-over" point. It is not IF they are going to leak, it's when they are going to leak as it is a 100% given that they will. If this is the only viable option, then be sure that you realize that they need to be inspected annually (or more often), or changed out after every few years to be safe. A few examples below of perfectly good low hour engines that had a "wet riser" or something similar and when they failed internally, the owner was into the BIG bucks as to repair. |
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Destroyed Turbo are the results from the failed "wet riser" on the right. |
This "wet" riser failed in less that 700 total hours hitting the owners wallet big time. As mentioned, you NEVER want a wet riser cooled w/ salt water, even as "cool" as you might think they are. |
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8) When the vessel design is such you are very limited as to the physical dimensions of the exhaust size ( like installing a muffler in a confined space) and you need to reduce back pressure but you cannot install larger pipes, tubes, etc, another option would be to bypass some of the water that is normally mixed into the wet exhaust.
In most cases, the engine seawater system pumps more than enough water to cool the engine and sometimes as much as 2+ times water than needed to cool the exhaust.
This can vary as to engine design AND exhaust design, but bypassing approx 1/3 of the water that leaves the heat-exchanger or cooling system on the engine and sending it over the side of the boat can easily reduce back pressure by 1" Hg or more in some cases.
An added benefit of this is that it can add a "visual" as to water flow and, in many boats, this would be a plus as the seawater water flow is sometimes impossible to determine. |
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Exhaust Water By-Pass - just before the mixing elbow. |
Port & Starboard Exhaust Bypass. |
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Knowing that you are pumping seawater always adds comfort to your experience. If this is something that you feel would be needed, use the services of a company that has a track record in this type of work as it would be time and effort well spent. |
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9) Reference sketches and ideas: |
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Sketch A - "Typical Underwater Exit Design" with Muffler AFT of Exit |
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Sketch B - Custom "twin outlet" lift muffler can be used when the existing main exhaust run is too small and cannot be upgraded easily - With a 5-6" inlet and two smaller outlets ( 3.5" - 4.5") this base design can safely be used in applications up to 400 HP. This system was recently incorporated into a 46 ft Chris Craft Romer 'gas to QSB' twin-engined repower of a when no other viable option was available. |
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Sketch C - Custom twin outlet lift muffler to underwater exit |
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Sketch D - Safe "Dry Exhaust Thru-Hull" Design |
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Sketch E - Typical Fiberglass Surge Tube Connection |
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Marine exhaust system design failures |
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1) New 44 FT power Cat from Australia with new 6LYA Yanmars. |
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The boat was sold here locally and on the first trip out to the islands in "prevailing weather," while fishing with the engine off and the boat bobbing up and down, both engines had the aft cylinders fill with salt water. Luckily the captain called me and I told him what he had to do to salvage the engines. That night after a long tow back to the dock, we pulled the injectors and flushed the cylinders out. The next month was spent re-doing the exhaust system ( about a $12K job). |
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When the captain looked in the engine room, he saw water dripping out of the turbo - Think he was in trouble? This was the vessels maiden "fishing" voyage. |
Custom Replacement Riser with temporary exhaust wrap - "Use all available height". |
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2) New 26 FT vessel with a Yanmar 6LPA and a Bravo #3 drive. |
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The stock riser was about 2" above flooding when brand new and within the first year, as the vessel got loaded with "gingerbread," the engine flooded at the dock. The engine was toast and the owner had to buy a complete NEW engine. |
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This shows the WL inside the factory riser. - Over the top or "spill over" point - What are they thinking ! |
"Toasted" Yanmar 6LPA 315 at 150 Hours - The builder did not believe in gravity or Cardinal Rule #1 |
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3) 3126 CAT Factory Wet Risers & result |
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These pictures show what is "typical" marine type couch engineering mixed with FACTORY salt water cooled wet risers that were installed on a 3126 CAT. The factory risers were made of Stainless Steel with the salt water inlet at the bottom of the riser. Two things happened over 4 years and 190 hours. Because the riser outlet at the top were designed and installed at such a "shallow down angle" (have seen this on new Mainships too), water would drip down the riser during cranking and after shut down damaging the turbo. After about 3 1/2 years/200 hours in service, the riser failed internally leading to total failure of the turbo and failure of the #6 cylinder exhaust valve. CAT later changed from Stainless Steel to Bronze construction for this design (that solved the "rotting out internally part" of this poor design) only to have the shallow angle of the outlet come back and bite them on many Mainship installs. It took CAT engineers about 7-8 years to understand the issue (gravity being the main culprit) and they finally dumped the entire design with the last generation of 3126 CAT's and the newer C-7's. |
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4) Factory wet elbow made from junk materials |
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If you recognize this design of a wet elbow on your boats exhaust system, I'd be checking the internal condition of it often after the first 3 or 4 years of "marine age", regardless of total engine hours.... |
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5) Results of a very poor design from a "builder" that wanted "NO INPUT" during the construction. |
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Original builders design and installation: Results of very poor design and "Mickey Mouse" exhaust wraps. On the maiden voyage and seatrial, engine room ceiling tile caught on fire. |
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Our Solution: A re-designed riser and mixer, proper clearances and supports, and 1st Class Exhaust Insulation on the dry sections. In the big scheme of things, this could have been an expensive learning curve. Guess who's wallet picked up the $6500 "redo" tab? Just like most of the time, the owner !! |
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6) Volvo Factory supplied wet mixer for a newer Volvo TAMD 120 |
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This is a Volvo Factory supplied wet mixer for a newer Volvo TAMD 120. At 800 hours and 4 years the owner was complaining about black smoke. We pulled the air cleaner and found the turbo was binding.. Noticed external water leaks on the factory supplied exhaust mixer and pulled it. The inside was also leaking and some rust was apparent on the exhaust turbine wheel w/ lots of crusty carbon/salt build up.. Cleaned it all up and installed a new "factory elbow" at the tune of $2800 each - he did not want a custom unit. The overall design, multiple pieces, and internal seams and welds says it all. Very poor design and he is sure to see the same failure again as the new elbow was of the same construction. In my opinion, the owner got off easy as it could have been a lot worse. |
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7) Lack of thought as to both raw water flow, dry riser design |
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These picture's are a perfect example of a design that may impress a buyer but shows a total lack of thought as to both raw water flow, dry riser design, and long term reliability and safety for the engine because of the "jacketed design" and orientation. Not only does the raw water input elbow go against any common sense as to water flow restriction, with the overall design with internal welds in the jacketed area, this elbow will fail and leak into the turbo when it does rot out internally (just a few years down the road at best). The supplier (a well respected popular engine distributor) should not be in this part of the business, or at least use a different company to design and build the exhaust mixers and risers. The first pair of supplied units were recalled for possible cracked welds. Just another sad example of "couch engineering". |
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This picture shows the initial design of the "factory". Within 50 hours cracks developed on the outside alerting the owner of a problem. Of course, it would never crack on the inside!! |
After this showed up, the "factory" distributor decided they needed to do something. They sent new mixers with a "Band-Aid" fix - Time will show that this is not a fix for an inherently very poor design. |
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"Fixed" replacement mixer. Add some gussets, a "Mickey Mouse" water inlet, polish it a touch and viola, the owner thinks he's OK... Remember, he didn't pay much for the fix, and he received the same - NOT MUCH!! |
Another view of the POS design of a "wet mixer". Why even waste the time & materials building such a piece. That's what I'm trying to figure out!! |
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8) Complex SS wet riser that the owner thought was "cool", but after 1 year of frustration and over $10,000 in repairs, he finally saw the light. |
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The designer/fabricator tried his best to make a buck - This riser was on a Detroit 650 HP 8V-92 and failed in two ways - The exhaust sprayer (inside pic) was clogging and the engine would either overheat or the raw water hose would burst - One time the burst hose took out a new Inverter. Then, after dealing with that issue (working with another local mechanic that had no clue) the unit failed internally and took out the turbo. About $10,000 later we finally got it fixed right. Moral of the story: Never never do you want a raw water jacketed riser !!! |
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9) This design went 3 months before the engine hydrauliced for the last time. |
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This builder thought for sure you could put the riser/turbo at the waterline, inject water in a jacketed riser that is close to level, and then push it up hill - Within 3 months and less than 25 hours the engine had water in the turbo and cylinders - Actually it probably had water in it the first day, but somehow the engine did survive for a couple of months... What was he thinking !!! |
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10) "Doomed" |
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This is another example of a repower job that cost a extra few bucks after someone thought they had it right. The "repower guy" seemed to think that exhaust systems could be plumbled like water pipe in a house and attempted to use the factory "one size fits all" cookie cutter wet elbow. He also forgot about gravity and within 2 weeks had starting problems. The turbo was getting washed daily with salt water... Designing a proper riser the first time around is always cheaper. |
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The water jet at the apex of the elbow, in the event of failure of the inner wall water would spill backward into the engine. By not having the port for the water jet along the downward angle of the elbow this design is doomed for failure. |
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11) Poorly designed wet mixers |
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These pictures depict what we see quite often with the CATAPILLAR factory wet elbows - Poorly designed wet mixers that "clog" unnecessarily due to a "couch engineered" design...With all the issues we have seen with the different type of CAT Factory wet risers and mixers, I really wonder where they hire their engineers from. |
We are here to help, so if you need anything, just drop us a note or post on the forums.
Tony Athens | October 1st, 2006
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Here are some pics to show you how some "out of the typical box" thinking can help in making the exhaust as it should be - Safe, practical, and politically correct for the vessel to allow an easy "get around engine room" and one that truly fits the installation.
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Starting with a "factory" inline muffler shape applicable to the install. |
Gathering the necessary "puzzle" pieces. |
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Outlet for muffler "dip tube" and side exhaust outlet. |
Building the custom mitered exhaust outlet tube to "fit" the boat. |
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Custom "dryriser" and muffler inlet design. |
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Getting the "hull" set up for an exhaust outlet. |
Side exhaust outlet tube mock-up - You need to protect the boat's LP paint job!! |
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Outlet flange building process on "mold-release" tape. |
COMPLETE !!! - notice the water bypass-this system showed under 25" H2O pressure at WOT and was "super" quiet... |
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We are here to help, so if you need anything, just drop us a note or post on the forums. |
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Dry Exhaust Designs and Ideas |
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Dry exhaust systems are not very common in the typical marine vessel used in recreational service. There are many reasons why you do not see them although, in many cases, they do have desirable features when designed and installed correctly. A dry exhaust system can add considerable costs, is usually more complex as to proper design, fabrication and installation, and can be a dangerous fire hazard if the design and installation is not 100%. What many operators and builders DO NOT understand is the approx 1/3 of the total energy (heat) that comes from the fuel that is consumed by a diesel engine is expelled as heat thru the exhaust system, and this heat must be contained and then exit the vessel safely. With a water cooled exhaust (wet systems), controlling and dissipating this heat is much simpler. |
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Commercial Fishing Vessel "Ocean Pearl" - Images above show shop construction, layout, and pre-assembly is time consuming but it's the only way. This "dry system" took about 60 man hours to design and fabricate. Images below show support brackets and installation. The under deck installaion took about 2 hours. |
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When looking at the pictures of dry exhaust systems, a few of the common design & installation features that you may notice are:
1) The use of stainless steel through-out the system when practical. 304L & 316L series stainless allow the use of lighter weight sections because it is not subject to the corrosion effects of diesel exhaust on the inside or corrosion on the outside from salt laden air. SS can operate at the continuous temperatures in the 700F to 1300 F range that diesel engines exhaust produce without losing strength or scaling. SS can tolerate these high temperatures without being cooled by large external air flows that trucks and other non-marine applications have. |
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Commercial Fishing Vessel "Saint Peter" - 28 Ft lobster vessel powered w/ a Cummins QSB. Images above - we had limited space but worked around what we had. We only had to "wrap" under the deck because of proper "drafting" of the muffler compartment. Images below show lower muffler support and our "unique" type of muffler supports that not only give a lot of adjustability but transfer close to zero heat to the nearby attachment surfaces. "Top hat" and upper stack that employs the same features. Expensive and time consuming to design and fabricate, but this is one place you DO NOT want to cut any corners. |
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2) Un-cooled exhaust piping "moves" or expands and the use of flexible "bellows" is mandatory. We use SS bellow made of 321 SS at it has shown to give long term reliable service in demanding high hour commercial application.
3) Under the deck is where most care must be taken as to spacing and supporting or "hanging" the system. You must allow enough space to install proper insulating blankets or covers and all support brackets must allow a minimum of heat transfer to the adjoining surfaces. |
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Cummins N-14 in the 75 Ft commercial seiner "Anthony G" with 5" dry outlet to 6" bellows and muffler. |
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4) Once the exhaust exits the deck and is now in the typical "muffler" compartment above the deck, the use of natural "drafting" from the heat is critical to safety. Ever wondered why the stacks on ocean liners are so large on the outside? That's because they use the heat that goes out the exhaust to "draft" the internal piping and engine room - just like a chimney, the heat draws excess air thru it.
5) Dry mufflers are large, heavy, can be quite cumbersome to deal with, and get extremely hot. The bracketing to hold and support a muffler on a vessel must not only be strong, it also must not transfer heat to the surrounding support surfaces. We always leave plenty of room in this area and allow the use of draft air to cool the support brackets. If the muffler compartment is large enough and well drafted, then using an insulating blanket around it is not necessary as the draft air becomes the insulator. But since each design is different, this is now an option based upon the uniqueness of the overall installation. |
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Cummins QSC w/ entire dry run and muffler support "on-engine". |
Simple John Deere 99 Kw generator and attachment to existing "under the deck" dry muffler - Installed on the 90 Ft, 300 Ton commercial long liner "Ventura II". |
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Hopefully if you are going dry, some of the designs and ideas we employ will help you build a safe and well constructed system.
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Some Thoughts on Underwater Exhaust Systems |
Underwater exhaust systems can offer many advantages (and some disadvantages) to the overall design on a boat. In some cases, going "underwater" may be the only choice in many applications because exhaust routing from the engine room to the stern is close to impossible, or good planning was not done during the initial design. Having underwater exhaust may seem like the ultimate way to go, simple, "it must be super quite", and "maybe I don't even need a muffler". Well, this is not the necessarily the case at all as going underwater adds another dimension to the exhaust system many builders soon find out at first seatrials. "RUMBLE"
Typically, underwater exhaust is what is normally referred to as "exhaust exiting" through the bottom of the boat, but in some cases, underwater exhaust could also be exhaust exiting at the transom or the side of the boat that is below the waterline. Since exhaust exiting at the transom (or on the side of the boat below the waterline) may or may not be "under water" when the boat is traveling forward I am confining this page to exhaust exiting thru the bottom of the boat, which is always under water. |
As many boat owners may have already figured out from personal experience, underwater exhaust may not be the perfect solution to noise control, although many with no experience in underwater exhaust always seem to think, "What could be a simpler way of muffling an engine's exhaust system." It seems that most underwater exhaust systems that I have seen in the last ten years have had issues with rumbling at low to medium speeds, causing a different type of "discomfort" in the confines of the vessel. Although the outside noise may be low, the exhaust energy that is dispersed beneath the vessel's hull can have a tendency to create a low frequency and very uncomfortable "rumble" or vibration inside the vessel at some speeds.
What we have learned about underwater exhaust in the past 20 years is that mufflers still need to be an integral part of the exhaust system so that the exhaust energy is reduced / absorbed before exiting the vessel.
Some advantages of underwater exhaust are that it allows the exhaust to exit in the engine room floor and not have to travel at its full size dimensions all the way to the transom. Over the years we have found many boats have no provisions for increasing the size of the exhaust piping aft of the engine room or is close to impossible to do, leaving us no choice but to exit the side of the vessel, OR, underwater. Sometimes we even use a combination of underwater and a stern exit / bypass. The exhaust system on any vessel needs to be carefully examined to see if an underwater solution is feasible, and / or is, the best alternative.
One of the main goals with any underwater exhaust system that can be used to the advantage of the vessel owner is the forward movement of the boat, in that it can and will create a low pressure area with the forward movement of the vessel keeping back pressure to a minimum when designed correctly. In many cases, this is a distinct advantage and allows a smaller size to be used which would go against most ideas as to how exhaust systems actually work.
Below are some pictures and a simple "outlet drawing" drawing showing the basic layout of a typical underwater exhaust system with a horizontal inline muffler that has been modified to operate vertically, and a smaller bypass muffler. Again, this is only a typical representation, as many times, a lift muffler is used as the main muffler before the underwater exit, as it can be the best choice for some applications. |
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Cummins QSM 670 UNDERWATER exhaust system. The system uses a 4" dry riser w/ 6" mixer, to a highly modified muffler, and under water outlet. Notice the 4" wet bypass to the transom that incorporates a small inline lift muffler - This particular system showed under 20" H2O exhaust pressure at WOT and was very quiet at all speeds. |
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4" bypass to side outlet |
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Underwater 8" outlet with 24" reverse scoop |
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Basic layout for this particular vessels exhaust system. When the builder designed this vessel, he left zero provisions for a conventional stern exhaust, so an "underwater" solution had to be found. |
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Starboard Exhaust for a 670 QSM - 4" Dry Riser to 6" wet mixer. |
Port Exhaust for a 670 QSM - 4" Dry Riser to 6" wet mixer. |
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Close-up of the Starboard riser/wet mixer to muffler connection. - Because of the short hose, a "double hump" was used for added flexibility and safety". |
Custom in-line heavily modified Centex muffler glassed into the vessel bottom. |
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In-line lift muffler makes for 4" low pressure by-pass to a side exit just before the transom. |
Base mock-up of port riser w/ measurement for a custom wrap. |
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And last is the most obvious criteria for any underwater exhaust design - With any underwater exhaust system, the exit thru the bottom of the vessel needs to be designed in such a way the it is no more vulnerable to cause an issue with as to hull damage, physical penetration, water intrusion, failure of components , or ? as the main hull itself. So leave this part of your vessel design or repower to a company or builder well versed in this type of work and has a proven long term record in building underwater exhaust systems. |
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Tony Athens | October 1st, 2006
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There are no REQUIRED exhaust sizes for Cummins marine engines; there are RECOMMENDED minimum sizes that may or may not meet the required exhaust restriction requirements published by Cummins. Those two statements above are also applicable to most marine engine recommendations / requirements. The sizes that are recommended are based on past experience and are merely a guide in the selection process for designing a safe and non-restrictive exhaust system. |
For all of the Cummins marine engines that are in current production, the maximum restriction at rated output is 3" Hg (about 1½ psi) and I believe this is close to most of the competitive manufactured turbo-charged engines in this 100-1000 hp range.
In most exhaust systems that are in the type of boats discussed in these forums (150-650 HP,) there are TWO distinct parts of the exhaust system/ piping. The DRY part and the WET part. Even on the factory "wet elbows" supplied by all of the manufacturers that I've seen, these two sections exist, though many people don't realize it.. The inner pipe of this "wet elbow" is actually a 90-degree dry bend, or section, surrounded by raw water to keep the surface cool. At the end of this "wet" elbow, where the exhaust hose attaches, is where the water is introduced (hence the term "mixing elbow") and the exhaust NOW becomes wet. Inside this elbow is a smaller diameter (typically around 2 ½ - 5" ID) which is the dry side, and where the hose attaches, it expands to (or is surrounded by) 4-8" tubing/OD piping, depending on the engine size, etc..
When using custom exhaust risers, or most factory supplied wet elbows, the fabricators of these systems employ various techniques to design and build these parts. Some of the designs follow good engineering practices with "thought out" design failure scenarios should the system NOT last the life of the boat. But, MANY do not. In practical thinking about marine exhaust systems, never consider your exhaust riser or wet elbow to be "lifetime." But, in real life, when most marine exhaust systems fail, (wet type), they lead to contingency damage of various engine parts as the designer DID NOT figure in a failure scenario that would (will) occur from internal corrosion/leaking. This is usually due to the fact that when the "wet side" fails (the failure is often in close proximity to where the salt water is first introduced to the exhaust riser/elbow,) this water ends up in the engine when the owner least suspects it. Internal failure of "wet elbows" and custom water jacketed risers is an old and ongoing problem, regardless of material choice, and/or other claimed construction features. |
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When building custom wet exhaust systems, these are but a few are of "common sense" guidelines to follow in their design that will help eliminate these types of failures/contingency damages: |
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1. Use all of the available height in the engine room for the riser (where needed and is practical) BEFORE turning over the top and injecting water; i.e. always inject the water on the downhill side, or down stream of the top of the riser. A wet exhaust system with a steep downward slope is always better and safer. |
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2. Always use gravity to your advantage. Water flows downhill so, if you have a system that holds water (water jacketed risers for instance) and this system fails internally (it's not IF it is going to fail, it's WHEN it fails,) where will the water go?? Into the turbo/exhaust manifold/cylinders?? Think about YOUR riser or elbow, should it fail internally where you can't see it., what might happen. |
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3.Be sure that IF the option presents itself in the design of a wet exhaust system, to allow for all of the water to drain itself from the exhaust when not running. Although this can't always be done, you can still build a safe system by utilizing other simple design ideas, custom mufflers, surge tubes, etc. |
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4.When sizing the system to meet acceptable restriction requirements in order to protect the engine from excessive back pressure, keep bends to a minimum, especially "wet" 90 degree bends. You can assume that, for any given size of piping, a smooth 90 degree "dry" elbow is equal to about 10 feet of the same diameter pipe as far as restriction goes. In some instances, wet 90s could easily be equal to 20 feet of piping when unnecessary water is injected into the exhaust. That brings us to one of the main reasons for this discussion: Exhaust sizes vs. restriction "requirements." |
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A typical high performance marine diesel of around 300 HP will pump about 50-70 GPM of salt water through the engine cooling circuit at rated RPM (not necessarily rated HP.) This large amount of water is needed to keep the engine cool and provide for some reserve, but all of this water (excess water) is NOT necessary to inject into the exhaust system to cool the exhaust gases and quiet the exhaust level.. Although most engine installations do indeed inject all of this water, as it "came from the factory that way," this is not required or necessarily desirable in many installations and repowers.
The mixing of salt water into the very hot exhaust gases accomplishes many things: |
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It cools the exhaust to levels that are safe (140 deg. F or less) allowing the use of hoses, fiberglass tubing and mufflers, and adds considerably to the quieting and scrubbing process. But it also adds considerably to the restriction of the exhaust system..
Although I've talked to "people in the know" that claim the opposite (the exhaust are gases cooled and therefore have less volume,) just believe me that when water is added to 900+++ degree exhaust and steam is produced, that the volume of the mixture of hot gas and water vapor is substantially higher, and therefore needs a much larger exhaust diameter after this mix takes place. This, along with the addition of the water itself and its own frictional resistance and volume within the piping, all add to back pressure and require larger piping than the dry side.. A simple way to see this is by looking at exhaust diameters of typical 300 HP diesels in trucks and comparing them to the typical sizes of a 300 HP marine diesel wet exhaust system.
Now, back to that excess water, and how can we use this water that is needed for the engine cooling but not necessarily needed for the exhaust cooling. First we need to understand how much "excess" there is and then how we use it to our advantage.. Just from testing and building wet and dry exhaust systems for about 20 years in boats, I've learned that you need to inject between ¾ and 1½ GPM of water flow per 10 HP into most any properly designed mixing elbow/wet exhaust system to allow for more than adequate cooling and silencing of the system.. By putting a simple "T" in the hose after the heat exchanger that goes between it and the mixing elbow, and then allowing the proper amount of water to flow out the side or back of the boat freely, one can reduce back pressure by a measurable margin, and now, in many cases, use smaller than recommended sizes of exhaust hose and/ or components and still meet restriction requirements.
From direct experience, I've used 5" wet on 450 C's and 4½" wet on 330 Diamonds and still was able to be well under restriction limits at rated HP and RPM. In quite a few of the repowers I run into, we are going from a gas motor w/ around 3 ½ or 4" exhaust size, and the recommended size for the new diesel may be 6".. This can be a tough one in many instances (space and cost limitations) and with some clever engineering, I've always been able to use 5", or even less in some cases.. There are many factors involved in this selection of smaller sizes, and only with experience to draw from, can all of needed design features be put together in a way that will insure a safe, but non-restrictive exhaust system. As to having to use 8" exhaust on the Cummins 450C (mentioned in a post on the Volvo 70's forum last week); only in an exhaust system with a design that gave little thought about all of the options which could be used to lower restriction, would an 8" exhaust size be needed. Never have I had to use an 8" exhaust on this engine to meet restriction requirements.
Please don't take the above to mean that I don't use 5", 6" or even 8" systems. I'm only trying to help with some of the repowers that come up where the recommended exhaust sizes DON'T fit the constraints of the boat or maybe the pocket book. It takes very careful planning to reduce from the recommended sizes but this alternative is there, if the design is right. There are many other tricks to reducing restriction in wet exhaust systems and these may include coring a hole through the first input baffle inside a typical inline muffler, enlarging spigot sizes on both the input and the output of an existing 4" or 5" muffler to the next larger size, etc. etc. etc. Again, these all come from past experience and field trials along with some good solid engineering.
And, as one added feature with bypassing some water out the side of the boat, you will get a easy "visual" of this water flow, and on boats w/ swim steps and stern exhaust, seeing this water flow can add a feeling of comfort knowing that you are pumping lots of seawater.
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The pics below show some designs that have accomplished the features mentioned above and were made to "fit the boat", the requirements of the applicable engine manufacturer, and used "common sense" as a component of the design. |
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Bertram 31 port engine |
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Dry / water cooled thru-deck |
Dry Riser-Rises 3 feet above water line before water injection |
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450 Diamond with 8" riser |
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330 Diamond V-Drive |
370 Diamond High Mount V-Drive 25Ft Farallon |
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Starboard Riser with custom muffler inlet / Cummins N-14 |
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Port Cross Over Cummins N-14 |
4BT Riser |
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Riser for "Too Close To Transom" |
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Under water 8" outlet |
First part of riser shown above with "FLEX" section
The top of this engine is 18" below the waterline "static" |
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Tony Athens | October 1st, 2006
Tony Athens | October 1st, 2006
The following pictures should help with understanding the Cummins aftercooler on both the B's and C's. These pictures are from a current 350 C and are basically identical to all of the C's including the earliest 400's. The "B's" are the same but shorter. The biggest problem with servicing these coolers is the disassembly because as time goes by, moisture causes corrosion between the brass and the aluminum at each end of the cooler, making the removal of the tube bundle difficult. In theory, the brass doesn't really touch the aluminum except "slightly" on the air side, but dirty moisture bridges the gap, and voila, the process starts. This is most prevalent on the bottom as this is where most of the moisture settles. The moisture comes from condensation (fresh water) and not from leakage (unless there is a problem).
WE start by removing the complete aftercooler from the engine and putting it a vise. Keep the cooler horizontal. Leaving the brackets on the cooler makes for a much easier place to hold it. Index both end caps BEFORE removal as this way you don't have to figure out later how they orientate. Remove the caps and remove the bundle. If your cooler has not been apart before, this can become a challenge. I sometimes have to use a block of wood, hammer, WD 40, etc., to get it loose/slide it out. Upon removal, you'll notice that the air intake side is much funkier that the air exit side. Sometimes, lots of black slimy sludge. This is somewhat normal, but varies from boat to boat. The fins are very fine and they act as a strainer, and between that, the cold seawater going thru the center causing condensation on the fins, miniscule amounts of oil mist that's just about always present in the engine room air, molecules of oil that leak past the turbo seals, dust, salt laden air, and ??, these aftercoolers can sometimes look very dirty. |
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In a Vise |
Cleaning tubes |
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The simplest way to clean the air side is to use spray brake cleaner (lots of it), let it soak and then spray the cooler w/ soap, Simple Green, or ??, and hose it clean. I 'd then use compressed air to blow out the excess water, or just shake it and let it drain/dry for awhile. Don't worry about some water left in the fins, it won't hurt the engine. Here in the shop, we have a tank filled up with a product similar to Simple Green and we boil the coolers for about 1 hour and then just rinse them. I DON'T recommend any type of acid on the air side. Clean/ rod out the tubes w/ a 3/16" aluminum rod and if they are excessively encrusted w/ calcium / salt / ?? deposits , you might consider using toilet bowl cleaner, on/in the tubes only. |
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Removal |
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Inside the aluminum housing , wipe it out with a solvent, and inspect both ends for corrosion. It will be there so don't get worried. Just use a 150 grit cloth and sand it somewhat smooth. Re-clean w/ solvent and now comes the assembly and the key to future servicing and longevity.....LUBE, and plenty of it. |
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Coating with grease |
Cap lube |
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Look at the pics again, and coat the first inch of each end of the cooler housing along with the flat end. Coat each end of the core and coat the inside beveled edge of the caps and flat surface. Lube the caps screws and the NEW "O" rings. Don't use old O rings as they become flat. You can buy these from any bearing house for a couple of bucks each.
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Re-assembly |
Insert all the way |
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On ALL new engines that leave Seaboard, we disassemble the new aftercoolers and lube them up as we know what happens down the road to a "dry" factory assembled aftercooler. Even on BRAND NEW coolers, we see the early signs of corrosion and if the factory would just listen to what I've been trying to tell them for at least 10 years now, lots of problems associated with servicing these coolers would disappear. They seem to think that a little oil or grease on the O ring is all that's needed. Another case of true couch engineering and the thought process that goes with it. |
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Installing O rings |
Tube orientation |
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Now its time to talk about your choice of lube/grease. I've tried many types over the years from marine greases, synthetic lubes, to Teflon based pipe dopes, and my favorite is now a product called "Alco Metalube". I've been using it for about 4 years now and have seen the results firsthand as we service these coolers 1-2 years after we've assembled them with this product. The coolers just slide apart ( an important reason to disassemble them horizontally) and any corrosion is kept to an absolute minimum. The stuff is a smooth white-ish green grease but weighs about twice as much as regular greases, and is the best product I've found for assembling aluminum to stainless, brass alloys that come in contact w/ aluminum, and threaded stainless or steel bolts used on a boat. Most truck type stores carry the product in S. Calif. If you can't find it, "Rigid" (the pipe people) make a great Teflon pipe dope that may be as good. In a pinch, just use a good marine wheel bearing grease or any type of grease that you think is "super".... Anything is better than dry....Just be liberal with the lube... |
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Everything lubed |
Final Assembly |
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Hope this helps and if you have a specific question, just post it and I'll do my best to help...Tony
P.S. As you can see from the "disasters", the aftercooler tells it all about what's going on in the engine room. Exhaust leaks, saltwater dripping on or near the intake air, impellers that fail, etc... |
Tony Athens | August 1st, 2006
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Yanmar 6LYA |
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6LY aftercooler-removed |
6LY aftercooler core as removed when new |
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6LY aftercooler on bench and apart |
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Ready for caps & O ring |
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Sliding in |
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End caps greased - ready to assemble |
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Tony Athens | August 1st, 2006
This is not in defense of CAT or anyone else referencing your total disgust for saltwater cooled aftercoolers that may use aluminum in part of their construction. It's just that maybe there might be other considerations involved here than just a defective design based SOLELY upon the use of the materials in question.
No matter how much design effort is put into a particular mechanical component, you can not have perfection in a design that will satisfy all the desired objectives. No choice of one design will cover "all the bases", as all designs have many objectives, with many of them "trades offs", as to overall initial cost, choice of materials, weight, acceptable design life, maintenance, etc. In the case of seawater cooled aftercoolers, CAT is not the only company that employs this system (SWAC), and is also NOT the only company that has chosen to use an aluminum alloy for the main part of the housing and/or components that typically have a copper alloy core inside of the housing with seawater passing thru the core. In fact, I cannot think of one diesel engine company manufacturing marine diesels under 12 liters of displacement developing above 50 HP per liter, that does not employ SWAC and that does not use aluminum in part of the construction of these seawater cooler aftercoolers.
With over 20 years of dealing with many styles of seawater cooled aftercoolers from all of the companies discussed on these forums, my opinion is that each company has employed "their" design that best meets their objectives and design criteria. ALL of these designs employ some type of "seal" and "insulator" system that keeps the seawater from bypassing the core and entering the engine. This same seal/insulator also keeps the water from contacting the air side of the system which is commonly made from an aluminum alloy and bridging the gap between the core and the housing. This is the small area (boundary) where the problems start to occur and where design and assembly make the unit more or less prone to failure.
I have found much fault with the SERCK coolers used on Cummins engines but can also say that with proper maintenance, these aluminum housed seawater cooled aftercoolers, which also have a copper alloy core, can outlast the engine. BUT, I can likewise say, without reservation, that they do have the potential for leakage from the seawater side to the air side (aluminum) and, depending upon all of the conditions present, engine failure can result.
In the case of the Cummins supplied seawater aftercoolers, the main fault doesn't lie strictly because they chose to use aluminum on the air side, but rather because of the assembly practice that is used for the component. This particular "design" relies solely on an "O" ring for this seal that keeps the seawater where it is supposed to be. Problem is though, the seal is only a very small boundary, dimensionally and, because of all of the variables in operation related to moisture on the air side (condensation) and seawater on the other side, the potential for pitting, corrosion, and worse (leakage) is an on-going potential problem. But, keeping this problem from happening is relatively easy. Just disassemble the aftercooler when new, and re-assemble it with copious amounts of the best marine grease you can get in the suspect areas*, and then do it every 1000 hours (or less) or every two years. By doing this, the potential for leakage and/or progressive corrosion is just about nil, and these aftercoolers made w/ aluminum and copper alloy can give good reliable service for well over 10 years (* there is a thread on this procedure w/ pics on these forums). Also, this particular design of aftercooler (water seals are located on the bottom and top), aggravates the issue as condensation on the air side sits at the bottom seal and is only separated from the seawater by about 1/16". Even though the condensation is fresh water, it still causes pitting and corrosion to the sealing surface on the aluminum housing. This is where "grease" really mitigates the problem and keeps it in check. If this design were flipped 90 degrees, much of this problem would not be there. Is any of this a "design flaw", that should start a "class action" law suit?? No, it's just one of the trade-off's in the overall design.
I'm not familiar w/ the CAT aftercooler, but maybe their particular "trick" design for maintaining seawater where it is supposed to be leaves something to be desired. But maybe they have some of the same couch engineers working for them that Cummins has, that have no real experience with servicing aftercoolers and understanding what really happens in their use when seawater is attempted to be held in place w/ a dry rubber seal. Possibly, just the application of the right grease when assembled new would solve much of the issue, but maybe not. I don't know in this case.
I have dissembled quite a few of Yanmar aftercoolers used on their smaller engines and one on a 4LH. They also use aluminum for the air side of the housing. BUT, they also "epoxy" ( at least it seems like some type of epoxy) the cores in the housings and I have yet to see one leak. Tough to service, if needed, but their "trick" doesn't seem to leak, and, seems to have good isolation for preventing galvanic corrosion or electrolysis. I also recently worked on a Volvo 41 series aftercooler and this one had plastic seawater caps, an aluminum housing and a brass/copper (?)alloy core. It was leaking, and we needed a new core. Overall, I did not like the design (the way it was "sealed"), as it seemed to have the potential for Murphy's Law to come into play during the assembly.
Generally, I would tend to disagree w/ you, Karl, as to the "law suit" thing, IF your sole contention is the use of aluminum as part of the construction in a saltwater cooled aftercooler. That doesn't mean I would not like to see all saltwater aftercoolers made from titanium, stainless, bronze, and cu-ni, I just think that the culprit ( if any) may be in a particular design flaw and/or assembly/maintenance practices, and NOT just because CAT chose to use some aluminum in the construction. Can you post some specifics as the actual design or construction, or do you happen to have a parts/assembly breakdown or technical drawing that can be scanned/posted??
Just my thoughts.
Tony
I did a good job passing Corrosion 101 years ago and since then have had enough experience in this field to make some qualified judgments as to design, functionality, and overall usefulness of marine engines and components in this field. I'd be the last person to argue that a cast titanium housing for sea water cooler aftercoolers would not be a superior choice of materials for this type of service. But I also realize that design is "give and take", and this is where I think you are missing the point. What you are really advocating, since you are adamant on this subject, is to take on all of the companies that use aluminum in their designs, Volvo, Cummins, Yanmar, MAN, MTU, etc.. As for the other "qualified" individuals you mention as "people of a like mind" supporting your feelings, well again, we all have our opinions. Mine is only based upon my own experiences and my reasoning for this posting is to help avoid some of the issues that come with the ownership of these types of engines. It's not to litigate my way into an replacement engine.
Also, if a properly chosen aluminum alloy is the wrong material, then what is the right material that would keep the costs competitive w/ what the market will bear, along with having ALL of the mechanical properties needed for this component? If the design life of the engine is 3000-7000 hours / 10-15 years of marine service, and the aftercooler made with an aluminum housing outlasts the engine in most cases w/ proper maintenance, then why go after the aftercooler design when it was a piston or valve that let go and took out the engine.
Karl, you are a very knowledgeable guy, but you are also a Detroit guy dealing w/ heavy iron. These engines we are talking about are in a different class, and I personally don't think the comparison is fair. The Cat 3208 at 375 HP built close to a 20 year track record with aluminum housed seawater cooled aftercoolers w/ probably only a handful of failures ( not that I even know of one). If the 425 CAT is experiencing many failures, then let's look at it as an individual flaw and not just categorize everything else built w/ similar material as trash. As for failures of other designs/makes of aftercoolers w/ aluminum housings, again I have not seen this issue unless it was related to poor maintenance or a flawed design that made the aluminum parts more susceptible to failure.
I'd also like to mention the following since you are so hung up on the galvanic series. There are 1000's of aluminum hulled crew boats in service all over the world and most of them have propellers, sea strainers and heat exchangers made of materials based on copper alloys. Certainly they have zincs and/or impressed voltage cathodic protection ( like aftercoolers) , but the fact remains that using aluminum and copper based alloys was the best trade-off in design. Should we start looking into premature hull failures and find a common denominator that has deep enough pockets to sue?? Again, I'm not saying that aluminum is the best material for making aftercooler housings - it's just the best compromise at this point in material design for this purpose. Maybe in a few years, a high strength / hi-temp engineering thermoset plastic will be the material of choice for these components. In the case of CAT and their issues, I would tend to treat that as a individual problem that needs to be dealt with. Aluminum has its place in the marine environment, it's just that it needs a little extra thought as to how and where it is used and how it is maintained to get the longevity in service that it can have. Tony
I'm not arguing w/ you as to the problems associated w/ aluminum and copper based alloys touching each other when immersed in seawater. The "copper penny" thing (a well know analogy) is a perfect example, and, in fact, all that needs to be part of that scenario is the right moisture and Father Time, total immersion is not even necessary. But, now take that copper penny and lay a 1" x 1" X 1/32" thick piece of common plastic ( a piece of milk carton for instance) between it and the aluminum hull. Problem basically gone, immersed or not.
The issue here is really whether the design of the aftercooler is such that isolation and sealing along w/ continuing long term proper maintenance can happen during the course of the useful life of the motor. If SERCK were to redesign the neck portion where the aftercooler core seals in the housing by adding a stepped plastic sleeve about 3/16" thick w/ a "O" ring groove in the aluminum housing, and an "O" ring under the bronze cap that squashes the whole thing together, I'd say that the useful life and possibility of failure would be nil for 20+ years even w/o the use of grease (although it should still be used). Plus, it would make maintenance much easier. This simple modification, early on, would cost close to nothing, and to change now would still be in the long term interests of all. I would call this an improved design or modification to an already reasonable design. Don't forget one of my motto's "ALWAYS LEAVE ROOM FOR IMPROVEMENT". In this case, SERCK has left that room and maybe CAT left too much room.
In Cats case, maybe their issue is with the way they chose to seal and isolate the components. Bad /defective design?? Very possible. Bad choice of materials, maybe, if the alloy of aluminum was wrong, and /or the overall design does allows contact between the two very opposite alloys in the presence of seawater (or fresh water for that matter).
So Karl, go ahead and rant and rave about aluminum and its use in these applications. Don't spend your time worrying about it, let me and the other people who are willing to re-educate themselves to deal w/ the potential issue. It is dealable!! Maybe Pascoe needs to look at this in a different light, instead of just condemning it all. Why doesn't he offer a suggestion as to improvement, instead of just complaining?? If I were you, I'd spend my energy looking at "that" engine you came close to upgrading to and buy them so you can really enjoy your boat. Once you experience replacing 40 year old diesel technology w/ a current a design, you may be willing to change some of your perspectives. Actually waiting a while was a good thing now that "common rail" is here. The experience is unbelievable compared to regular mechanical injection. But to do this, after you buy them, dissemble the aftercooler and use your knowledge to reassemble / modify it to keep it sealed and isolated for the next 10-20 years, or longer. There are some amazing greases and assembly sealants available today that can easily accomplish this task. After that, I think we will both do better, have more time to go fishing, and stand a better chance of keeping the lawyers out of our lives and our pocket books. Tony
You have worn me out and I'm sure you want to get on too. But your efforts have paid off as you have convinced me that you will never be a candidate for repower because no manufacturer of an marine engine today of this class (or any class?) could offer you what you want. You need that 8 -10+++ pounds of iron per horsepower as it probably does give you most of the features you mentioned. So forgiving are those old Detroit's.
As for JML and his problem, hopefully he will be able to get this worked out w/ CAT. With a service bulletin on his side, I have no idea why he is getting the run around. But, with so many eyes watching these forums now, I suspect he'll come out whole in the long run.
Tony Athens | August 1st, 2006
The air around us contains vast amounts of moisture. It's always there and the amount averages (leaving out the extremes of the world) from about 30% to 75% measured in relative humidity. Of course, if you are like me, the term "relative humidity" kinda relates to how uncomfortable I feel in the middle of a hot day and is not much use in the practical life of diesel engines. Or, you might just say "Relative to What?" What I like is this term "Absolute humidity," which is a measure of the amount of moisture in the air; OR the weight of water vapor per unit volume of air.
What we all need to really understand is how much water is actually in the air around us. I'll try to explain it this way, at least this is the way it makes some sense to me.
A typical modern turbocharged diesel producing 300 HP will consume about 1500 CFM of air at this HP output level. Ambient air at 80 F can hold about 35 grams of water per cubic meter of volume at 100% saturation (got that from a chart from a lecture at UC a while back)... On a typical nasty late 80 degree F afternoon when the humidity is at 70%, that would work out to about 2 1/4 lbs of water vapor being consumed by the engine per minute running at 300 HP output (check my calcs to be sure I didn't screw up). Now, let's take that "captive air" that's being fed from the turbo through the seawater cooled aftercooler. When the hot air touches the relatively cool tubes/fins , you have a perfect medium for a percentage of that air to cool sufficiently to reach its dew point and condense on the tubes/fins and form water droplets which can (and do) fall to bottom of the aftercooler housing (don't forget, for air to condense, you MUST have a surface for it to attach to). But also realize, even if it didn't condense, the engine is still eating this water without harm (the water is in the air anyway), but under the right conditions, the water droplets form in the aftercooler and sits there until the conditions are right for it to go back into a vapor form and get fed to the engine again, and again. This process is a continual one and at times, the aftercooler on a Cummins 6CTA 8.3 may have about 3-5 ounces of "loose" water" in it, and then, that water will just "go away."
During the course of our business we service about 2-3 aftercoolers per month, and many of these servicings happen the morning after the customer worked the entire previous day, came into the harbor late w/ the sun going down, he had just come off "plane" and idled to his slip for 5-10 minutes before shutting down.. Next morning he removes the cooler and brings it to me. This seems to be the case when we can find a few ounces of water in the coolers (tip it over and it spills out). I've had to show many customers that this is NOT salt water (a leak) but "condensation"......I just taste it in front of them and offer the same.........Usually, no takers...
Anyway, the water in the aftercooler is sometimes there, and sometimes not . But it's always in the air and it doesn't hurt the engine. As far as a "drain hole" (ala Volvo)?? May have some value and I've wondered about a small leak/weep hole in the right spot on a Cummins aftercooler many times. It's not the water going into the engine that bothers me, it's the water sitting in the aftercooler causing unnecessary corrosion. But of course, that's a another topic for the couch engineers that designed an aftercooler with many preventable design flaws that can lead to less than a long term life, especially with less than a prescribed sensible and applicable maintenance schedule in the O&M manual furnished w/ these engines.
Tony Athens | August 1st, 2006
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