overheating?

[muskyman64]

bought a 77 Johnson 25hp, was misfiring and discovered a cracked coil and also believe the head gasket was bad and replaced that. Motor ran fine but seemed to run hot. put in a new impeller and thermostat all new gaskets, pumps water strong. Took the motor out to the lake and ran for about an hour, 3/4 to full throttle at about 10minute intervals then down to idle after each interval. At idle after running high speed it would stop pumping water for 15-20 seconds or so and blow steam out the pee hole then start pumping water again. Water coming out of pee hole is plenty hot, I can keep my hand in the water coming out pee hole but it is very hot. Motor doesn't seem like it wants to quit, like it is overheating. spark plug color looks normal. I have two older mercury 20hp (70, 74) they never stop pumping water. Cant say I ever put my hand in the mercury water to see if that was that hot.
any thoughts ?

 

[joereeves]

Water exiting water telltale fitting should be warm but not excessively hot.

Drop the lower unit to check your work. Make sure the plate is sealed to the lower unit and that the impeller housing is sealed to the plate to eliminate any possibility of the pump drawing air. On the boat, the cavitation plate should be approximately 3/4" below the bottom of the boat.

Note that a scored impeller plate can, and usually does, cause the pump to create an air pocket. Also using a pitted or scored impeller housing is not a good idea.