How to check a thermostat.

[quack1]

Buddys 9.9 overheated and he replaced impeller and thermostat. There is water coming out the indicator hole, but the motor still heats up. I suggested to put the thermostat in hot water and see if the plunger moves to test it. We tried the old and new thermostat and nothing moved on either. Is there another way to test the thermostat?
Thanks

[boats.net]

To test the thermostat you have to set the temp side in water, heat the water and watch the thermometer to see at what temp the thermostat opens.

[quack1]

Thanks. That brings up another question. About what water temp range should open the thermostat? It is very possible we didn't have the water hot enough.

[boats.net]

Need to know what model number of outbaord it is.

[quack1]

The model number is J10RLETM

[boats.net]

140 degrees is the normal operating temp for that engine.