Wanted For Free: Yanmar 3GM30F overheating?

[Rhubarbx3]

TaShiba 31, Jacksonville Florida. The 3-cylinder started immediately, but after 7 minutes the overheat alarm came on. New thermostat - same outcome & hot to touch. Removed the thermostat altogether and the motor runs as it should with no alarm. Thermostat location is not overly hot. Question: - Can I run the engine constantly without a thermostat with no harm to the engine?

[roverhi]

It will run ok but not at max efficiency. Would replace at first convenient opportunity if testing it shows it’s defective. Put it in a pot of water on the stove and watch to see if it opens before the water boils.

[bgallinger]

Roverhi got it right, but I would add a couple things: 1) Check the impellor 2) Check the heat exchanger 3) Check the thru-hull to be sure it is clear and 4) Check the intake
screen is clear of weeds!!!!!!!

[svJasmine]

Must check the exhaust elbow. These engines will restrict the flow after a while.