Rebuild or not to rebuild

[Yamahaha]

1990 200 ETXD. The powerhead is off the lower unit, getting ready to replace the control arm and shift rod. The manifold extension and exhaust guide parts will also have to be replaced. The big question is the condition of the surface of the powerhead where it aligns with the exhaust guide (and gasket in between). The powerhead surface is somewhat pitted from salt corrosion on approx 50% of the surface.Three part question: What's the probability of the gasket and "gasket goo" effectively sealing these surfaces. What type of goo do I use. What happens if it doesn't seal effectively and salt water intrudes into the area between the power head and the exhaust manifold?

[boats.net]

The primary places to seal is the exhaust port and the water cooling port in the middle of housing. You can use high temp RVT sealant or any good sealer.