yeah, there was no water in the thermostat housing. So it could have been hotter than read

Ok, the bad news is here. Checked the first bank of cylinders, 1 good, 2 full of water, 1 light grey plug. However, compression looks good. 180lbs all cylinders. What is likely the damage? Exhaust manifold gasket? Please help inform and direct me what to do!

Could be a cracked exhaust manifold if you have water in one of the cylinders.

I wrecked an engine with a bad header. Filled one cylinder with water, then at started up it would hydraulic and it blew the head gasket out btween two cylinders. It still ran, but sounded like crap. I was to young to care. I eventualy had to repair the head and block.

It was running ok, not 100%, but 95%. Hard start though after a good run, assuming water leaking into cylinders from exhaust gasket. Otherwise boat got on plane and ran well. I hope I can get this fixed without pulling the boat out of the water or the motor out of the boat.
Ti confirm, compression looks good, no water in oil. Just water in cylinders, both banks. Intake gasket? Exhaust manifold gasket?

I say cracked Exhaust manifold filling the cylinders when you shut it off. Sorry

I vote for this as well. Water in cylinders is never a good thing.

no, never a good thing, but is a cracked exhaust manifold really difficult to fix. Correct me if I'm wrong, but a couple new manifolds and gaskets and I should be off to the races again!

As long as that water didn't do any damage like hydro lock or break a valve/valve seat. But since you've ran it already, I'm guessing you'll be OK.

both banks have water in them, would that not indicate a intake gasket failure as opposed to a exhaust manifolds? Would it be likely that both cracked. Sorry for all the questions, trying to learn and understand, try to fix it myself.

If you want the "easy" way out, get some Revolution exhaust. They are the least expensive "performance" exhaust. But the real reason (at least for me) to get them is the manifold/riser joint is dry, so there is no chance for the joint to leak into your motor.

I bought them. I got them for about $1K, which is about twice what new stock style manifolds/risers will run you. cheap peace of mind for me.

Either way, this is not something I would mess around with. Replace everything on both sides, because the next time water gets into your cylinders it could destroy your motor.