1983 Mercury 150hp High RPM’s overheat

[Themanofsteel]

I have a new impeller, new poppet diaphragm, new thermostats, Hoses clear, yet the overheat alarms goes off at high RPMS. Water seems to be coming out of the water hole strong and steady.

The engine does feel very hot to the touch. Thought it might me the sending unit which I took off of a 1998 120 Force engine.

Water flows steadily from the start from the pic. Is that normal?

 

[racerone]

Leaking head gaskets can cause overheating as well.

 

[Themanofsteel]

Would I see a leak at the head gasket?

 

[racerone]

????-----No ----Combustion gasses would leak into the water jacket.----More pressure than the pump can make.-----Compression test might " see " the leakage.

 

[Themanofsteel]

Thanks

 

[Themanofsteel]

I replaced the head gasket and also cleaned the system with salt terminator. After which the engine ran good up to 4000 RPM’s (25mph) but any higher then that and the overheat alarm triggers again.

Also on a different issue, something funny happens when I throttle a little more than half way, the engine slowly fades and eventually dies. If I give it full throttle it runs steady. If I give it 1/4 throttle it runs steady.

 

[Dukedog]

Thought it might me the sending unit which I took off of a 1998 120 Force engine.

get rid of this and get an oem sensor ta start with.....