1998 Force 120 overheating under load

[Tatum.david]

I have a 1998 force 120 temp alarm goes off once the motor is in the water and under load. It will idle for 10 plus minutes no issue. I replaced the thermostat and impeller and I do have a solid stream coming out of the pisser. I did a compression test tonight and found the following:
(These were done with the engine cold I’m going to do one tomorrow night warm)
#1 cylinder 150 psi
#2 cylinder 150 psi
#3 cylinder 165 psi
#4cylinder 160 psi

I also have oil in the small recirculating lines, I put a clear hose so I could see if I had water flowing through there.

Is it possible the head gasket is bad and when up to operating temps oil from the gas mixture leaks into the recirculating lines? My only other thought is if there is a crack in the block and water is getting into the cylinders causing it to overheat. Or the temp sensor is bad? Does anyone know how to test the temp sensor I don’t want to just throw parts at it.

 

[racerone]

Oil is supposed to be in the recirculation hoses.

 

[Tatum.david]

Would you know how to test the temp sensor with a dmm? What temps cause certain resistance

 

[topgun3690]

Could get an IR laser thermometer and see what the head temp is....handy tool to have anyway.

 

[Nordin]

Do as topgun3690 says, use a IR thermometer and "shoot" at the head when the alarm goes off.
You can test the sensor but hard to get an exactly value when it goes off (bimetal switch).
Put it in a can with water and heat it up on a stove, check with a VOM when the switch close and check the temperature.