Yanmar 2gm20f temp creeping up

[Wotname]

FWIW, I did have a Yanmar thermostat (2GM20) that was stuck about 2/3 open and without a temperature gauge, I never knew until one day on a whim, I pulled it out to test it on the bench. So it was running quite cold for some time and I wasn't aware of it.

[Compass790]

Don't worry about it too much, plenty of raw water cooled engines have a long life.
It's just you might as well use the benefits of fresh water coolings higher temp if you have the hardware.

[wmcunninghamii]

As a follow up, I did take the boat out on a 40 mile round trip motor. I ran at 3000 RPM. The motor came up to about 160 (as observed at my water temp meter) and basically sat there for the duration. I guess I needed to have the confidence I was not overheating the engine before I was ready to let er rip. But it looks like I am OK.

The other thing I noted was heat soak when I stopped the engine. I had a little emergency on the return leg and stopped the motor with no cool down. Sure enough, the block temp spiked to about 180 degrees. from 160 while running.

I was in the satellite industry before I retired. We would carefully monitor thruster flange temperature after completing a firing to ensure it did not exceed temperature limits. The flange would continue to increase in temp even though fuel combustion had terminated. If it looked like it was going to overheat we would do a short "quench" firing which would flow some cold fuel through the nozzle to cool it down. Seems counterintuitive but it worked great. The only way to do that in a diesel would be to restart which was not happening in my circumstance.

One comment was made earlier in the thread about confusing combustion gas temp with block temp. Could someone explain this to me? I do realize the exhaust manifold is very hot and is not indicative if engine operating temp but am not sure this is what the poster was getting at?

[Wotname]

Originally Posted by wmcunninghamii

.......
One comment was made earlier in the thread about confusing combustion gas temp with block temp. Could someone explain this to me? I do realize the exhaust manifold is very hot and is not indicative if engine operating temp but am not sure this is what the poster was getting at?

That would be me (most likely)

Someone posted that the engine should be run hot enough to "clean out the carbon" or something like that. While this is true, it is the combustion gas temperature and the cylinder pressure that cleans out the carbon, not the block temperature.

So you could run the engine relatively lightly loaded and the thermostat will keep the coolant temperature at (say) 160F. However carbon might be (will be?) building up as the combustion temps and pressures will remain low.

Run the engine under load at (say) 80% of max rpm and the combustion temps and pressures will be much higher and yet the thermostat will keep the block temperature at (say) 160F. The higher combustion temps and pressures will clear much of the carbon.

Check the Yanmar operation manual for "racing" the engine periodically if operating at low rpm and low loads for long periods.

If you are interested, check the oil temperatures by using a IR temperature gun (hand held) aimed on the oil filter. You will be surprised how long it takes for the oil temperature to stabilise when the engine is run at higher loads.

[wmcunninghamii]

Originally Posted by Wotname

That would be me (most likely)

Someone posted that the engine should be run hot enough to "clean out the carbon" or something like that. While this is true, it is the combustion gas temperature and the cylinder pressure that cleans out the carbon, not the block temperature.

So you could run the engine relatively lightly loaded and the thermostat will keep the coolant temperature at (say) 160F. However carbon might be (will be?) building up as the combustion temps and pressures will remain low.

Run the engine under load at (say) 80% of max rpm and the combustion temps and pressures will be much higher and yet the thermostat will keep the block temperature at (say) 160F. The higher combustion temps and pressures will clear much of the carbon.

Check the Yanmar operation manual for "racing" the engine periodically if operating at low rpm and low loads for long periods.

If you are interested, check the oil temperatures by using a IR temperature gun (hand held) aimed on the oil filter. You will be surprised how long it takes for the oil temperature to stabilise when the engine is run at higher loads.

Oh, got it. Thanks, that makes sense. I am glad I asked. Very interesting and better describes what the term "running hot" means in terms of carbon reduction.

I have an IR gun, I will do some trending on the oil filter just to check that out.