Cummins Fuel cooler removal

Has anyone removed their fuel cooler on a Cummins 5.9 in a warm water climate? I have an immense amount of respect for Seaboard Marine and Tony Athens, and have read their position on this / watched the video. My engine runs at 1500 RPM, not pushed hard, however my sea water temp is close to 90 F in the summer. I like the idea of simplifying, but recognize my environmental reality.

If anyone has done this I would love to hear your results.

Generally I would go with Tony's recommendation, but in his area the Pacific sea water temps are probably 25 degrees cooler than yours.

Why don't you measure the fuel temps at the Racor before and after cruising all day. If they stay below 100 F you should be ok.

David

Thanks David, that's a great recommendation. I did email Tony - he got back to me promptly saying that while every situation is different, it would probably be fine in my use case. I will measure the temps the next time I'm out.

I did it a couple of years ago. Getting all that plumbing our of the way made servicing the raw water impeller sooo much easier. Of course, Maine waters are not known for being particularly warm.

I would think it depends on where your tanks are. It they are in a hot engine room then you might want to keep them, but if located away from the engine the general consensus is you can do without it. I’m considering removing mine, or at least one of them.

I should have included more information. I have a single QSB 230 HP. Dual 200 gal tanks on each side of the engine. But it is HOT down here

I appreciate the comments, and will check temps on my next run and report back.

What’s the motivation for removing the cooler?

I’m actually thinking of ADDING a cooler, all to reduce engine room temps. Over time the heated return fuel heats up the fuel tank, and all that heat radiates into the ER.

twistedtree said:

What’s the motivation for removing the cooler?

I’m actually thinking of ADDING a cooler, all to reduce engine room temps. Over time the heated return fuel heats up the fuel tank, and all that heat radiates into the ER.

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Reduce points of failure and ease access to water pump for impeller change.

There are millions of diesels working in plus 100 F conditions with no harmful effects due hot fuel. The better question, to Cummins and Tony, is what fuel temperature is considered problematic. Also it is engine model and boat specific.


Failed fuel coolers are not a pleasant experience so your question is a good one. If you stick with it I’d suggest a 5 year throw away cycle.

Boat diesel is a great site to chase down this question. Not to mention there boat loads of us with no Cummins or fuel cooler whether located in the tropics or not.

The fuel cooler becomes LESS effective the warmer the seawater temperatures are, not More effective.

Think about it... In colder seawater temperatures the fuel cooler has colder water around it, making it work better. In warmer temperatures the reverse is true.

Mine are removed and I really like the access it's removal provides to the seawater pumps for servicing.

ksanders said:

The fuel cooler becomes LESS effective the warmer the seawater temperatures are, not More effective.

Think about it... In colder seawater temperatures the fuel cooler has colder water around it, making it work better. In warmer temperatures the reverse is true.

Mine are removed and I really like the access it's removal provides to the seawater pumps for servicing.

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I get this and if I were back in the pacific northwest with this boat and engine, the fuel cooler would be gone. Our raw water temps range from ~60 - 90, so my question is, although less effective, will removing that source altogether be problematic. That's a rhetorical question. I will head over to Boat Diesel - thanks for that recommendation Sunchaser.

Just looking at this logically, I agree with Kevin. Higher water temps will mean a smaller drop in fuel temp using the cooler therefore less reason to use one not more reason. Also, the warmer water temps should not affect much if at all fuel temp with no cooler compared to operating say in the PNW (where the cooler water will lower the fuel temp more with a fuel cooler) as the water does not really come into contact with the fuel (except through the tank contacting the hull). Air temp may have a slight affect as higher temps could warm the fuel sitting in the tanks a bit? It seems logical that the fuel temperature difference (after removal of the fuel cooler) would be less with operating in the "non-cooling" warmer water, so the risk of "issues" would be higher if removing it in cooler waters???

I removed the fuel cooler on my Cummins 6BTA 330hp and was very happy with the results. Much easier access to the impeller, less possible failure points, and no worries about the disaster that a fuel cooler failure could cause by adding saltwater to your engine's fuel supply or by restricting raw water flow for engine cooling!
Before removal, I would do the research you are doing just to be sure, but it makes sense to me that you should experience no ill effects if you do.

You and Kevin are correct, Tom. Thank you for having the patience to walk me through it, as Kevin tried to do. I never said I was a quick study, but I do study

FWIW, I have wanted to remove my fuel cooler for a while, I just haven't gotten around to doing it yet.



Another consideration is how much fuel do you normally keep in your tanks? If your tanks are 1/4 full, and run on only one tank at a time, then you are heating up 50 gallons of fuel. If your tanks are 1/2 full, that is 100 gallons of fuel. That is double the heat sink. So if you are running for very long days on the same tank, your fuel temp would rise more than short trips, with full tanks, where you are switching back and forth between tanks.

Just my 2 cents worth.
When we cruised the PNW I never had any issue’s with heat in the engine room. So much so, that very seldom did I turn on the blowers in the engine room.

Cruising down south this past couple of seasons changed everything. We noticed the heat build up in the engine room by as much as 35-50 degree’s over that we experienced up north, and so the blowers were on almost all times. We struggled to get the ER temp below 130 degrees. The heat in the Er caused our low pressure pump on the water maker, the fuel polisher motor to shut down during use and the temp of the fuel tanks was significantly higher than before also. We carry 1,000 gals of fuel when full and as the volume decreases I suspect the temp of the fuel tanks increased. If I was using the water maker or fuel polisher ( this was to transfer fuel not really to polish) I would put a 120 AC fan directing the air to the motor.
So, to answer your question, if you are cruising in an area where the water temp is significantly warmer, I wouldn’t recommend removing the cooler. It might be Ok if your cruising the Florida area, but farther down the southern Lats might not be such a good idea.

Hope that makes since.

I only have the QSC 500 performance sheet at hand, but it gives some insight. Max allowed fuel temp coming into the pump is 140F. That seems pretty warm, but the catch is looking at the return fuel temp. It's 185F average. The key here is that high pressure fuel system as commonly found in engines newer than about 2007 heat up the return fuel quite a bit, and that needs to be dealt with. Adding a fuel cooler is the way Cummins addresses this, rather than leave it to the boat builder's engineering depart, which is usually an empty room.


If you remove the cooler, that hot return fuel will heat the fuel in your fuel tank. Some of that will get dissipated into the engine room, surrounding boat structure, and the surrounding water. So you have heat coming in at one rate, and heat going out at a different rate, but almost certainly slower than it's coming in.


To me, it's telling that Cummins includes fuel coolers as standard equipment. Personally, before removing it, I'd look hard at ways to relocate it.

Or maybe look at some blowers like Delta to evacuate some of the heat in the engine room. Draw air from the top of the engine room. If you can get the ambient air temperature down that will help and then maybe you can get away without the fuel coolers.

It seems to me the only reason to remove it would be fear of failure and/or access to other components. On my QSB it was not in the way of anything you'd normally need to access, however fear of failure caused me to replace it with the newest Cummins version. In the original style on my boat (2006) there was an internal double walled tube soldered at each end, soldered connections for in and out, such that failure seemed likely. The new version (which I found for somewhat less than SBMar's elimination kit) the seawater tube just goes straight through, there is an external jacket for fuel with fittings. it could still fail and leak some fuel, but is far less likely to leak seawater into the fuel, which would be problematic. The failure paths for that to happen are nearly eliminated. So that is an option for you.

Interesting that the Cummins QSB 6.7 doesn’t have a fuel cooler. It’s essentially the same engine as the OP’s 5.9, just a little newer.

Not for me. I run in hot summer water at 2800-3000 RPM returning 12-13 GPH that is used in part to cool the oil via an internal engine cooler. Tanks hard by the engine. Not having a fuel cooler could be a serious issue.

Fletcher500 said:

Interesting that the Cummins QSB 6.7 doesn’t have a fuel cooler. It’s essentially the same engine as the OP’s 5.9, just a little newer.

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Does it not? On the QSB 5.9, the fuel cooler is listed as a option, the installer could order it with or without. Is the 6.7 the same?

DDW said:

Does it not? On the QSB 5.9, the fuel cooler is listed as a option, the installer could order it with or without. Is the 6.7 the same?

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No one asked me if I wanted a fuel cooler when I spec’d this engine for the boat build. I don't see one noted on the Cummins 6.7 Drawings. I would assume they wanted to avoid the use of salt water cooling, and designed the engine with that in mind. 3 1/2 seasons, 550 hours, and knock wood all is good. Currently 5 miles offshore Del Mar, putting along at 7.5 Kns as I type this. Love this engine.

Fletcher500 said:

No one asked me if I wanted a fuel cooler when I spec’d this engine for the boat build. I don't see one noted on the Cummins 6.7 Drawings. I would assume they wanted to avoid the use of salt water cooling, and designed the engine with that in mind. 3 1/2 seasons, 550 hours, and knock wood all is good. Currently 5 miles offshore Del Mar, putting along at 7.5 Kns as I type this. Love this engine.

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Some years ago I seem to recall Tony’s comments on the 6.7 design mentioned a rethink of the need for a raw water fuel cooler. Cummins does listen to user comments and concerns. Have you talked to Tony on this subject?

sunchaser said:

Some years ago I seem to recall Tony’s comments on the 6.7 design mentioned a rethink of the need for a raw water fuel cooler. Cummins does listen to user comments and concerns. Have you talked to Tony on this subject?

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Hi Sunchaser, no I have not. I have only talked to Tony on one occasion and that was about 4 years ago when I was looking at a used boat with a Cummins. He charged me $150 per hour or so to go over various questions I had, and it was worth every Penney even though I passed on the boat. The guys in the shop will talk to me for free when I have had some quick questions, but they are not famous.

I am not implying the lack of a fuel cooler on the 6.7 is relevant to the 5.9.

I agree with Firehoser75; I removed the fuel cooler from my 37 Nordic Tug and maintenance is so much easier. My tanks are separated by a bulkhead so they don’t get hot from the ER. We live in Beaufort, SC and have had no issues. Took two hours total using Tony’s kit.

Any of you guys want to send me your abandoned cooler?

You are welcome to my old one if you want it. Worked fine when removed, but the new style seemed less likely to fail.

Captain Doug said:

I agree with Firehoser75; I removed the fuel cooler from my 37 Nordic Tug and maintenance is so much easier. My tanks are separated by a bulkhead so they don’t get hot from the ER. We live in Beaufort, SC and have had no issues. Took two hours total using Tony’s kit.

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Captain Doug - do you have a 6BTA or QSB?

I have 6BTA's on a Bayliner 4788. I also boat in very warm water in the summertime (90+ degrees). My engine room will often top 120 degrees. My fuel tanks are just forward of the engine area but it still gets warm there. I debated removing the fuel coolers a few years ago when I was replacing my raw water pumps. I opted to replace them rather than remove them under the general assumption of "better to do what's necessary to keep all that diesel from getting too hot". The cost of the replacement was not that much. I replaced the coolers and the associated hoses. All parts sourced from Seaboard Marine.

There are 2 issues as others have mentioned; fuel temp and engine room temp. The first (and easiest) item I would address is finding out exactly what your engine room temp is say after a good 2 hour run. If its higher than recommended then removing the cooler would only exacerbate that issue. If its lower then its on to investigating what the temp is of your fuel when it gets sent back into the engine and what the guidelines are around that.

I have a QSB 5.9 and the fuel cooler has not been an issue for me as far as access goes to things like the impeller. Personally, I would not remove it; but rather remove any cooler on the engine every 5 years or so and have them looked at.