Skipper, disregarding the reduced power and the wisp of smoke or steam you observed: Given your certainty that the raw water side of the cooling system is working fine and that your exhaust is not restricted the rapid rise in coolant temperature indicates poor heat exchange from coolant to raw water - most likely your heat exchanger on the engine coolant side, or the coolant hoses, or the thermostat. Less likely would be the engine's coolant pump not providing flow. There's many ways to inspect or test for blockage and flow, at the return from exchanger to the block for example.I know 165 is normal.
I said it built to 165 way too fast.
Like 4 times too fast.
And I said the water heater built too fast too. It would have trended to overheat had I let it run under load like I was, after the water heater obsorbed the initial heat.
Trust me. Intimate with the boat for years. Fuel and cooling systems are fine.
Sorry did not see your HX post #29. Did your test of that include actual coolant flow out of the exchanger with the engine warm - i.e. did you include thermostat opening and coolant pump performance?
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