Oil Coolers Needed?

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Roger Long

Roger Long

Senior Member
Joined
Jul 14, 2015
Messages
451
Location
Albany
Vessel Name
Gypsy Star
Vessel Make
Gulf Star 43
Like many vessels of her vintage, our Gulfstar 43 has absurdly large engines. At our normal cruise, each of the 1977 vintage naturally aspirated Perkins 6.354’s is only producing about 30 of its rated 130 horsepower. I run the boat hard for 10-20 minutes ever day or so but even at WOT, the engines would only be producing about half their rated horsepower. These particular engines seem quite happy with this operating profile. The exhaust is about the cleanest I have ever seen, oil analysis is good, the oil retains its amber color, and the dipstick markings can be seen through it even after more than 100 hours.

The dual raw water oil coolers which serve both the Velvet Drive transmissions and the engines are trouble just waiting to happen. My question: Is there any reason not to just disconnect the RW and bypass the coolers with this power profile? Many engines have no coolers at all and there would be some cooling just from the oil circulating through them. Another option might be to replace them with automotive air cooled units.

Please spare me the usual, “I don’t know anything about this but I wouldn’t mess.” type replies. Real world experience or pointers to where I could get solid technical advice on this would be appreciated.
 
The engine oil might be OK not cooled, but what are your tranny temps like?

Most of the advice I have received is dont eliminate them, but make them coolant cooled/warmed (in reality regulated to preffered op temps).
 
Last edited:
psneeld said:
The engine oil might be OK not cooled, but what are your tranny temps like?
Click to expand...

Good question. I just remembered that I have a remote reading thermometer on board. I should shoot the oil in line and maybe try bypassing and taking the measurement again.
 
I have wondered about this myself. I raced cars for years and there we ran at red line all the time in the middle of summer. Obviously had oil coolers and oil temp gauges.
In our diesel application running at very slow rpm and power settings it’s difficult to conceive of modern oil being remotely stressed especially with 4 or 5 gallons of oil in the sump. Diesels produce more heat than gas engines so there could be some issues there but it’s hard to conceive given the over all cooling efficiency of raw water and would be easy to verify with a harbor freight infrared temp reader.
Transmissions are a whole different story, definitely need the cooler to keep temps from breaking down the oil/fluid and keeping temps stable.
All just IMO

tbtapper
 
I'd second tbtapper on the trans coolers. I've checked inlet and outflow lines on both oil and trans coolers on our turboed 6.3544ms and they're usually 10-15 deg F higher before the cooler. This is at similar, light loads (~1500 rpm). I could see all the coolant in there taking care of the oil but the trans gets pretty warm even with the coolers working!

I'm interested to hear what you come up with though! Good luck!


-Gabe
 
Greetings,
Mr. RL. "I don’t know anything about this but why?" You note this system is "...trouble just waiting to happen..." but so are a lot of other things aboard. You can probably eliminate the oil cooler if you want BUT there must have been a reason they were installed in the first place. Why change it if it ain't broke? We have cupro nickel coolers and other than changing them every XXX hours, it's a set and forget deal IMO. Yes, I've heard anecdotal tales of cooler failure resulting in destruction of engines and transmissions but how often does that happen with a properly serviced motor which you seem to have?

Is your quest for elimination to simplify the system? IF you do eliminate the cooler will you be placing a screen in line to trap any bits of water pump impeller in case of a failure of same?
 
Oops! I didn't think this through before posting. Since the coolers are on the suction side of the RW pump, there is no way a leak could let sea water into the oil. I guess I should be the one to say, "I don't know anything about this but don't mess." Thanks to all and apologies for wasting your time.
 
200w.gif


Awww. Just when it was getting good...
 
I still am mystified why sea water cooled engines run salt water through the oil coolers etc.? As soon as you keel cool an engine, coolant is run through these coolers and the incidence of corrosion and the chance of cross-contamination goes to zero. Keel cooled engines don't bake toast or explode with coolant-cooled engines, why not just re-plumb and run coolant through the engine oil and transmission oil coolers? You would have to calculate whether the existing engine heat exchanger is adequate but you could add a second if necessary. The engine heat exchanger is a nuisance if it fails but it will not kill the engine if it fails like a failed oil cooler will. You will still have to run the waste salt water out through the exhaust so that part won't change. The oil temperatures in the engine and transmission will be perfect if the coolant temperature is within limits.
This would simplify maintenance and lower costs too, with a caveat that you "might" need a larger engine cooler or a larger water pump.
 
Roger Long said:
Oops! I didn't think this through before posting. Since the coolers are on the suction side of the RW pump,.
Click to expand...

Doesn't this mean your coolers are between the raw water pump and the through hull valve?
 
Greetings,
Mr. X. Now, THERE'S an interesting question, to be sure. Makes a heck of a lot of sense. Oversize the heat exchanger, if necessary, and cool everything via appropriate plumbing. GOOD idea. DAYUM!!! Yet another thing to add to the "list". Thanks a lot (NOT). Have a drink, in any case...

th
 
Xsbank said:
I still am mystified why sea water cooled engines run salt water through the oil coolers etc.? As soon as you keel cool an engine, coolant is run through these coolers and the incidence of corrosion and the chance of cross-contamination goes to zero. Keel cooled engines don't bake toast or explode with coolant-cooled engines, why not just re-plumb and run coolant through the engine oil and transmission oil coolers? You would have to calculate whether the existing engine heat exchanger is adequate but you could add a second if necessary. The engine heat exchanger is a nuisance if it fails but it will not kill the engine if it fails like a failed oil cooler will. You will still have to run the waste salt water out through the exhaust so that part won't change. The oil temperatures in the engine and transmission will be perfect if the coolant temperature is within limits.
This would simplify maintenance and lower costs too, with a caveat that you "might" need a larger engine cooler or a larger water pump.
Click to expand...

if I'm not mistaken my American diesel uses the coolant loop for the engine oil cooler but uses raw water for the trans oil cooler. It's half way there.
 
Am Diesel has a cooler/kit to change over to coolant cooled.

They do NOT recommend coolant cooled tranny cooler. At least when I called.
 
Funny they only recommend half...my Cummins has engine oil, transmission and turbocharger cooled by coolant but my keel cooler is my entire keel so I have no idea its capacity, it is not a commercial unit with specifications I can check. I can, however, run WOT for 24 hours a day and it won't overheat (seems very frantic, rushing about at 10 knots but the noise is horrendous) but I did have to get a larger coolant overflow tank because the coolant expanded considerably when I ran WOT and it overflowed - now I'm totally contained with a repurposed dragster fuel tank [made out of TIG-welded aluminum 8^)].

Heat exchangers are readily available and there are many quality-made non-Chinesium coolers out there if you have to add some more capacity.

RT, you're using my likeness without my permission...wait...uh...oh...right. Disregard.
A real British pub is my happy place. I wish we had such a civilized way to have a pint without being shouted at or music-ed to death in my country. And a pint of bitter has not much alcohol so you can drink a delicious pint with friends and not get sloppy or stupid. Or you can drink numerous pints and get sloppy and stupid and happy, if you wish. Long live the British pub!
 
One last thing, if you insist on using a transmission oil cooler with salt, take it off and replace it with a spare every few years and have the take-off serviced. Losing a trans cooler will ruin your fun and will cost you a lot.
 
sunchaser said:
Doesn't this mean your coolers are between the raw water pump and the through hull valve?
Click to expand...
,

Yes. Seacock > strainer > engine oil/transmission cooler > RW pump > engine.
 
psneeld said:
Am Diesel has a cooler/kit to change over to coolant cooled.

They do NOT recommend coolant cooled tranny cooler. At least when I called.
Click to expand...
Probably because engine coolant runs around 200F [93C], which is the same neighborhood as the engine oil, but hydraulic systems normally run around 140F [60C], give or take, and we try to keep continuous-duty gear reducers at or below that temperature range.

We used to design for oil-to-air hydraulic coolers in front of diesel engine radiators in custom builds (pusher fans, but a low delta-T) in high hp hydraulic system applications, so the hydraulic oil cooler gets the cooler air. The jacket water radiator would be oversized as well as the fan, but with Tier IV engines and aftercoolers and the EPA and such, we use separate heat exchangers now with their own fans so we don't have to deal with complicated combination heat exchanger packages and approvals and so on; easier just to use the factory package and find a place to put a big hydraulic cooler and fan. This is industrial/construction industry stuff, but the fluids don't know the difference.

Just a guess on my part.
 
Roger Long said:
Like many vessels of her vintage, our Gulfstar 43 has absurdly large engines. At our normal cruise, each of the 1977 vintage naturally aspirated Perkins 6.354’s is only producing about 30 of its rated 130 horsepower. I run the boat hard for 10-20 minutes ever day or so but even at WOT, the engines would only be producing about half their rated horsepower. These particular engines seem quite happy with this operating profile. The exhaust is about the cleanest I have ever seen, oil analysis is good, the oil retains its amber color, and the dipstick markings can be seen through it even after more than 100 hours.

The dual raw water oil coolers which serve both the Velvet Drive transmissions and the engines are trouble just waiting to happen. My question: Is there any reason not to just disconnect the RW and bypass the coolers with this power profile? Many engines have no coolers at all and there would be some cooling just from the oil circulating through them. Another option might be to replace them with automotive air cooled units.

Please spare me the usual, “I don’t know anything about this but I wouldn’t mess.” type replies. Real world experience or pointers to where I could get solid technical advice on this would be appreciated.
Click to expand...

When an engineer designs cooling systems, they need to worry with close to "worst case". Part of that equation is the raw water temperature. There are parts of the world with sea temps at 90 deg F at the surface. The FL keys is close to that in the summer. In our neck of the woods, the highest temperature at the surface is closer to 72. That is to your benefit with this idea. The other is torque and speed into the transmission. I ran my VD's at up to 4400 rpm in my last boat, and they did not run hot. Running 2000 is less stress, although the torque plays heavily here also.

question: why is WOT at only half power setting? Under or over pitched?
 
WOT should be about 1 or 2 hundred RPM below rated maximum. WOT at half power setting makes no sense.

Coolant temperature rarely gets above 170 degrees and look at the plate on your gears, its usually rated well above that.
 
Input from a matine engineer to clear something up in the discussion....


"A diesel can be about twice as thermally efficient as a gas engine. That means that for the same horsepower delivered to the shaft a diesel may convert nearly twice as much heat into power than a gas engine. The heat not converted to power in either engine is transferred to the cooling water or surrounding air so if both gas and diesel have the same power output the gas engine may produce nearly twice the heat as a diesel. A transmission has no idea of what is spinning its shafts and the heat it produces is related to the power in vs power out."
 
If the oil leaving the tranny is under 240F with the cooler in the fresh water system , it would work for me.

This boat is like most cruisers, way over powered, so going with the reality of the current installation and operating profile seems safe enough.
 
Xsbank said:
WOT should be about 1 or 2 hundred RPM below rated maximum. WOT at half power setting makes no sense.
Click to expand...

The power installations of many or most trawlers of this vintage make no sense. Oversized engines were installed for marketing reasons and because reduction gears with the proper ratio were expensive and hard to obtain when trawlers suddenly became popular. The boat is seriously under propped so the governer maxes out at about 50% power. The props are the best compromise for the speeds we like to operate at, 7-8 knots, S/L 1.12 - 1.28, 1400 - 1600 RPM, 33-56 HP (18 - 28 each engine).

Going slowly through the long no wake zones of the ICW and harbors would become harder if we added pitch to the props.

When I was designing research vessels like these,

Roger Long Boat Designer and Sailor

Engine suppliers would generally insist on the engine turning within 50 rpm of maximum at WOT if you wanted a guarantee. Modern engines are a lot less forgiving though than the Perkins museum pieces we have.
 
Roger Long said:
The power installations of many or most trawlers of this vintage make no sense. Oversized engines were installed for marketing reasons and because reduction gears with the proper ratio were expensive and hard to obtain when trawlers suddenly became popular. The boat is seriously under propped so the governer maxes out at about 50% power. The props are the best compromise for the speeds we like to operate at, 7-8 knots, S/L 1.12 - 1.28, 1400 - 1600 RPM, 33-56 HP (18 - 28 each engine).

Going slowly through the long no wake zones of the ICW and harbors would become harder if we added pitch to the props.

When I was designing research vessels like these,

Roger Long Boat Designer and Sailor

Engine suppliers would generally insist on the engine turning within 50 rpm of maximum at WOT if you wanted a guarantee. Modern engines are a lot less forgiving though than the Perkins museum pieces we have.
Click to expand...

I suppose you get that "neck snapping acceleration" with that low pitch. :D

But seriously, I'm going to suppose that 50% power is at a point much more than 50% RPM on the prop curve? And, more to your point; trying to use that unavailable 50% is generally fruitless in a FD trawler, with typically supplied engines.
 
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