OMC Sterndrive overheating

[Devildawgusmc_1]

I have a 77 OMC Stern Drive 400. 120 HP. I can't get this boat to stop overheating. I have replaced the impeller and assembly, water circulating pump, thermostat and thermostat housing. I don't know what else it could be. Please HELP.....

 

[Don S]

Re: OMC Sterndrive overheating

For the cooliing system to work, water must flow thru the engine, thru the exhaust manifold and exhaust elbow, and out the back of the boat.
Any hose, the block, manifold or elbow could be pluged up with rust, dirt, corrosion, anything.
Exhaust systems are a common place for blockage.