Originally Posted by Kyle
Unless your risers are ruined it would be real hard for water to get through the exhaust into the cylinders.
The boat flooded on a trailer in a field. There is no way for the water to flood up the riser and enter from the exhaust valves.
I would bet water entered through the throttle body filling the intake.
When at rest the intake valves could be opened or closed fully or slightly depending on where the engine stopped and which cam lobe was open or shutting.
I'm very concerned about the valves and intake. I can only imagine that they are real rusty.
I also am concerned on the cylinder walls. If water was in there a few days it would not bother me. This boat sat there for a LONG time.
Personally I would pull it and rebuild it no matter the results of the compression test. You will know its good then. The last thing you want to do is totally destroy it. Just ask around. I ruined a block and threw a rod through the side of it trashing the entire rotating assembly, breaking the cam in 5 places, totally ruined my distributor, and bent 5 valves.
Worst case you punch it .030 over but you may be able to get away with honing the block and resurfacing the crank.
It's worth spending some "unnecessary" money today than spending 4-6k on a new engine or whatever you would spend trying to buy used and hoping it will work.
Did the compression check , first 2 were 40 and 60psi ,so no point in going any further down that route, removed the throttle body only to find loads of rust , so will pull the engine to bits .
Thanks for the advise Kyle , helped make my decision on the correct way to repair .
Pictures coming later.