Well, after some poking around I think I can say I have a bad exhaust valve. After running at fast idle for about 20 minutes, the temps are at about 140deg F. If I put my hands on the risers the starbord engine and the outboard port riser are the same, warm to the touch but I can keep my hand on them. The bad head (cyl#3 inboard) riser is hotter and I can't really keep my hand on it too long. They are all new risers from Marine Manifold. So if my theory is correct the combustion stroke is going directly into the exhaust causing the slightly hotter exahust. If the intake valve were bad, I think the engine would be missing or popping. If the rings were bad there would be a sign of smoke in the exaust. Does all this make sense? Anyway I will wait until the boat is covered and winterized before I start the tear down. Besides, I have a honeydo list to complete before I turn a wrench on that project.
Here is the offending beast. Seems a shame to tear it all apart after the oil cooler and riser job last year.
I'm off to Holland for a week on business. Have a good weekend.
George