454 mercruiser running hot "update"

Unloaded RPM over 3000 -DON'T DO THAT!!

Your over propped - fix that first. Go for 4200 at WOT
 
What is that, about a 1 1/4" or 1 1/2" heater hose? Can you get a bronze 3 way valve?

Sounds like the solution.
 
Will have to check, but I "think" it was 5/8" or 3/4" hose, wont get back in there untill this week end.

Prop is the original mercrusier put on it, it was not changed.............D.........
 
I was thinking a direct flow thru using a large diameter would cause less restriction. Is it on the input side of the heat exchanger or off one of the exhaust manifolds. The size would point to the manifold.
 
Went back and reviewed the pictures to confirm, one side off the water pump, the other went to the intake manafold..........D........
 
Don't want to put a damper on things but I honestly don't think the heater is your problem. Think about it. My boat has the same set up as yours on my port motor. My stb motor has plugs in those ports. If your heater lines are plugged, then it is working the same as a motor with no external loop.
Al
 
Al, cant deny you could be right, but I spent a grand chasing it and never found any smoking gun. Then I find where the inlet to the heat exchanger of the water heater is almost totally plugged off, which is part of the cooling circuit to the intake. This is really the first time I have found anything that even came close. I reviewed the cooling circuit diagram and sure enough you are right, they plug those if they don't have the water heater or cabin heater, I have both. Down side is, I haven't found anything else that could cause it to run a little more than it should...........D...........
 
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