Home › Forum › Ask A Member › Leaking crankcase leads to overheat condition? › Re: Leaking crankcase leads to overheat condition?
I pulled them out yesterday evening (the J6’s). They had white blisters on the electrodes. This morning I put new J6’s in and ran at 5500 rpm in the test tank with a test wheel for 5 mins straight closely monitoring with a heat gun. It was doing the same thing as when I had it on the boat yesterday. So I switched to J4’s and that seems to have corrected things.
My only hesitation is the fact that I pulled the thermostat and it is running fine, but again, there are no clogs I could find in the cooling system anywhere. This thing is pumping a ton of water.
I don’t think the thermostat is/was the issue, because the cylinder head and thermostat orifice never even reached 143° (opening point of the t-stat). The cylinders were getting hot (170°-ish) but only at sustained WOT. So my summation is that the plugs were too hot, and were the culprit.