running hot

[57belair]

I have a 1979 Mercury 115 horsepower motor that starts right up and stays running for about five minutes and then shuts down. I have replaced all the spark plugs, wires, fuel pump, water pump, carburators, and fuel lines. I have put a tub of water under the prop plus muffs and it will barely pee and when it does, it is like steam not actual water spitting out. I have fed weed eater line through the pee hole and all I can get to come out is steam. When the water pump was replaced, a garden hose was fed through the bottom and achieved great pee. Does this motor have a poppit and if so where is it because I can not find reference to it in my manual.

 

[WillyBWright]

Re: running hot

Kinda sounds like a cracked block. Exhaust gas leaking into the cooling system, keeping water from reaching the powerhead. But it could be a simple blockage that isn't allowing water to reach it. Blockages can usually be backflushed out, but sometimes something gets lodged in the baseplate under the powerhead where the water tube enters from below, and sometimes the powerhead becomes packed with sand or mud.

 

[emckelvy]

Re: running hot

Could be a problem with the exhaust manfold inner baffle cover, the water jacket cover around the exhaust ports, or bad manifold gaskets. Might be time to pull the exhaust manifold covers for inspection.

First it might not be a bad idea to pull the back cover on the block (cyl block water jacket cover) and inspect for silt/debris buildup as WillyB mentioned.

HTH........ed