I read that's a clean dropout. If it looks like you switching off the ignition (like a cut out) then most likely it's in your ignition system. You are also talking about the temperature. It only appears after warming up. When the engine is running move your cables a bit. Also the connection...
The ticking noise is now gone? If you're sure of a leaking gasket then change it. If the intake is leaking it can also cause back firing. When it warms up the gap can get bigger and if the choke is working it's getting more fuel when the engine is cold. When the engine heats up choke is coming...
Reacting on water is indeed not good. I would start to check the spark cables for a good connection. Especially the one from the coil. Or replacing the coil. The rattling should be gone. You where also talking about a leak in the intake gasket. When a engine is warm the gap can extend. If there...
For me it sounds like the coil is loosing his spark to a ground peace(ticking sounds) is it possible to look at it when it's dark? Maybe you can see where the sparks is ticking over.
If it's possible to get a peace of color from the boat. Then go to a big car paint shop. Normally they have a color scanner. At least over here in the Netherlands is pretty common to use a color scanner.
