Yanmar 1GM10 Thermostat and Temp Sending Unit

[karluk]

I have a 1GM10. I replaced the strainer, thermostat, impeller, and all hoses after purchasing the vessel last fall. For 3 weeks this season, the motor ran fine at 2400 RPM for extended periods. It was negelected and sat in salt water prior to my purchase. I flushed the engine continuously prior to replacing all the parts. The exhaust elbow appeared slightly corroded, but sound. I started overheating last weekend after running at 2000 RPM for 10 minutes. Pulled the thermostat to check for obstruction (none) and the temperature sending unit to check operation. The thermostat opens fully at 125F. The sending unit switches at 150F. Are these temperatures too cool? Automotive thermostats generally are 160F to 180F (although they are pressurized systems and the Yanmar is raw water cooled and not pressurized). I have ordered a new exhaust elbow to try next. Any other suggestions?

[mitiempo]

The thermostat for a raw water cooled Yanmar should be 140 F. Any warmer and salt deposits will form in the cooling passages.
Fresh water cooled engines run at 160 to 180.

You say the exhaust elbow seemed corroded. Did you remove it to see if it is clogged?

[badsanta]

How clean is the bottom and the prop? That can cause an extra load

[JimsCAL]

As Brian says, raw water cooled engines are designed to run at about 140F to minimize scaling of the engine cooling passages. Do you have a good water flow out of the exhaust? If not, you have a restriction somewhere in the cooling circuit.

[tabnabtoo]

It could well be the injection elbow,and obviously you've checked the strainer but make sure the skin fitting is not blocked with seaweed,plastic bag old condom etc.etc. Good luck.