Yanmar Diesel overheating puzzle

[deblen]

Check the hose(s) between seacock,raw water filter & water pump">raw water pump for collapsing during high rpm. (suction side of system).
/ Len

[boeing1]

being raw water cooled I thing I would accomplish a engine flush first, with saltaway or other product, when was the last time you flushed the engine

[SouthernPride]

Sometimes the seacock looks ok but the flap sticks. Add a piece of clear behind the peacock, engine side, and watch or replace the peacock for good measure.

[Gamecock Rob]

I had a tractor diesel continually overheat on me but the temperature would rise slowly to overheating temp. Turns out the head gasket had a pinhole in it forcing hot gas into the water jacket. It was pretty simple to replace the head gasket. If you have a torque wrench and a battery powered impac gun(love my ryobi btw) it's not bad at all.

I hope it turns out to be something simple for you.

[Symphony]

Please post the solution when you fix this problem.

[Terra Nova]

Originally Posted by Mariellec

...Took apart the water pump (twice) - it looked fine, but I did replace the impeller...

This looks like your problem.

You took it apart (TWICE!) and changed the impeller, but you didn't bother to replace the "cams" and cover plate.