Everything I have heard, and my experience with my 1979 2QM20, is that the
QM Yanmars are among the coolest running diesels ever built. It's kind of a
mystery how they manage to diesel at all. Still, my engine runs perfectly
30 years after it was built. If I had just spent thousands to repower, I
would be estatic with it's performance.

I took my old thermostat out after three seasons and it failed the heating
water in a pan test. The engine had been running fine though. Engine
vibration not present in the pan on the stove may have been helping it
along. I put in a new thermostat and have detected absolutely no change in
engine performance or exhaust color.

Smile, sail, be happy, don't worry. Point the laser temp gauge at your wife
or girlfriend instead and make some wisecracks to see where they lead.

--
Roger Long