My stepson's 1988 mcm 7.4 liter, (ser# H013445), LH, marine Stainless manifolds and risers, raw water cooled, early Bravo 1, (ser# OB804538). This thing is in Maine, mostly in the brackish rivers. He went out into the open saltwater last season, it overheated, so he went to the nearest ramp, and called a pal to come get it. He said maybe 30 minutes total hot time. He said 'it didn't get really hot'. He said he checked the oil, saw the coffe colored mess, pumped it out, put fresh oil in, ran just long enough to circulate it. He says he fogged it, drained the water jackets, and put it away. I said I'd take a crack at it. I tried to pump that bilge out of the block, but I got more water than oil, maybe 2 quarts. Call me a cynic, but the only diagnostically useful info I think I have is that it got hot, and now the oil and water are fraternizing. I made a block off plate with a schraeder valve, and a pressure gauge, bolted it up where the t-stat housing goes on the intake manifold. I plugged the fat hose from the raw water pump, put 15 psi to it. It leaked down to about 8psi in 10 minutes, still had 5 40 minutes later. I rolled a stiff paper funnel for use as an ear trumpet to help me hear, and locate any hissing. Bupkiss. Just nothing. Should I have plugged the hose from the power steering/oil cooler to circulating pump?
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