Thermostat. 72 johnson 50 hp. 50esl72

[nitefisher]

Still need help! Please! I think I might have it narrowed down, but not sure. Ive workd on hundreds of boats/motors this is the first this has happend. I have a brand new thermostat installed in motor, I have checked it in a pot hot boiling water it works fine opens at 140 deg and fully opened at 143 deg. BUT! it seems as though it will not open when in the motor. I know for a fact that the water pump works left the thermostat out then ran it quik. could the thermostat be defective if it passes the pot test? I am using a flusher not a barrel or water tank.

[boats.net]

I assume you are having an overheat problem, sounds like thermostat is ok but do need to run it in water and not on hose flusher to properly test cooling system.

[nitefisher]

OK, I drilled and tapped the cylinder and installed a pee hole just for precaution, i ran it in a body of water the motor peed the whole time the CYLINDERS cooled, BUT the head still seems to be hot.