Cummin's Operating Temp

[Asureyez]

On the Cummins 6CTA8.3M-3 I've got 160 deg. thermostats in the engines as stock from the factory.

On the Boat Diesel board the reigning experts make strong recommendations to move the Thermo's up to 180 degree for better overall performance.

Reasoning runs back to the 90's when the early blocks were marinized truck engines and a lot of trouble was developed early with cylinder wall failure due to over heating (Thin Wall Blocks). While Cummmins responded to this issue with real time changes in block design they bought some time and switched out the installed base and new in production engines 180 degree Thermos with new 160' degree models to get better cooling at the low end.

When the new design was settled, the 160 degree thermos were maintained, but is not an ideal temp for the engine and the experts claim the old 180 degree thermos should be reinstated.

So should these engines be run at the higher temperatures?

On my pair they rarely touch 170 and then only when RPMS exceed 2300 and then its only on the STB engine. At WOT, temps on both will rise up to 190's.

I maybe missing something, but wouldn't a 180 degree thermostat be much ado about nothing?

 

[fwebster]

One of the symptoms of a diesel running cool is excessive smoke which is unburned fuel so the smoke is blue/black. If you don't see smoke and your transom stays clean, I'd say stop trying to fix stuff that ain't broke and go boating!

I've got a Cummins 4C in a dozer.....c-series, but 4 cylinders and no turbo......... and until that thing gets hot, not just warm, but hot like under a sustained load, you can't hardly see where you are going for all the smoke.

 

[WFYB]

I agree with Frank, I run the 160 deg thermostats in my boat. Same location - Ft Lauderdale. I see 160+ at idle 175 at cruise. I never see above 180 unless something is plugged or broken. My transom is clean and I only smoke when I first put her on plane going out the inlet.

One other observation - 190 seems high to me - You may want to check your strainer, impeller then heat exchangers in that order. I saw 190 at WOT on one of my engines about two years ago. About a month later I saw 200. We traced the issue to a zinc that had broken loose and partially plugged the starboard transmission heat exchanger. I serviced all 4 heat exchangers and the temp dropped back as noted above.