HELP!! Force 35 overheating

[Rickf]

Pontoon boat and motor have been together for 25 years, older 35 hp Force long shaft 357f7a overheating at wot: quick run down
started with would not run above idle, it backfired, ck reed valves ok, replace fuel pump, plugs, fuel and tank, compression at that time was 105 & 110, did a decarbon and ran great, water pump was putting out, engine was staying cool. Went for a run heard a pinging noise and shut down engine, overheated bad, melted wires, repaired. Would still turn by hand when got back to dock, let cool till next day cold compression test 75 & 80 low but would still run, figured water pump, went bought new one, dropped lower unit pump was still good - cracks for 10 years not bad, now what? It did not appear to have spun on the shaft. Installed new one anyhow. There was no thermostat installed, pulled head, no scoring or blown head gasket, pulled ex cover all ports were open no debris no even a piece of sand, intake area on foot was clear, I was running in open water.

I still have the engine apart, the intake water tube is fine no holes, intake screen clean and lower unit clean.

What am I overlooking?? any Ideas

Worse part its a friends boat and I'm trying to help him, and its in the water no trailer.

Thanks in advance for your input.

Rick

 

[kkelley]

Re: HELP!! Force 35 overheating

my motor did the exact same thing at low speeds it would pump water at wot motor went down due to heat. The impeller needs replacing from what i am told, mine was not cracked or torn but would not pump sufficent water to cool motor. By the way i have the exact motor you have take the old impeller with you to get a new one they are a little smaller. Due to the shaft being changed out on the motor it will not interchange with the 45 and 55 hp motors.