Reply To: 64 Johnson 5.5 hp Powerhead Base Gasket Problem

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June 22, 2020 at 4:21 pm #206426
Mumbles
Participant

    You might have a leaky or blown head gasket allowing combustion gases to get into the water jacket. Combustion pressure is much higher than any water pump can produce and the gases will force the water out of the cooling system causing an overheat situation.