Before my ownership it was run with (i believe) a non functional automotive style thermostat in the stock, late housing with no restriction on the side plate. In this mode the temp would never come off the stop, but I suspect that was a false reading and it was probably running quite warm as it blew a head gasket not long after I purchased the boat.
I have tried clamping the 1/2" hose before the thermostat to see if it made any difference and it did not. I've done some simple electrical diagnostics and nothing jumps out at me. I've also shot the head with an IR gun and all the temps look OK there. Obviously I won't see any fast fluctuations there due to the thermal mass of the head.
These fluctuations move quick enough (like 5-10 seconds from 200 down to 170) that I do suspect some sort of problem with the thermostat or the gauge.
Quote:
Originally Posted by sastanley
Aaron, I agree with joe...Take out the t-stat and see how it runs...if you don't totally tear apart the gasket in the process, you can just bolt the housing back on for the test, and maybe use some Permatex (#3 in the can with a brush) to help seal the gasket area and report back.
200°F is not too hot, but you are running out of margin much past that..most RWC'd motors are 150-170°F.
Do you already have the bypass valve on the 1/2" hose from the side plate that goes into the stbd side of the t-stat housing? You can simulate a valve (closing the flow in the bypass hose) to force the water up thru the block and t-stat housing with a pair of needle nose vice grips or similar tool.
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