I have a 1973 Johnson 6hp. I can't seal the thermostat cover on top of the head without it leaking water. I polished both surfaces with glass and emery cloth, used a new gasket, OMC gasket sealing compound (also tried without), and torqued to 85 in-lbs. It is leaking both towards the spark plugs and towards the flywheel. If I tighten it any more the gasket crushes. How can I get this to seal? I haven't tried RTV silicone but I've read about people using that. Do I need to let the gasket sealing compound or RTV cure for a certain amount of time to prevent leaks?
