Is my engine dead?

[vic008]

Fully endorse Ballsall.Head off then get mechanic to inspect all.
Keep us informed please

[Scubaseas]

Originally Posted by Carl-T705

If you ran the engine long enough without coolant to seize the engine you did damage to it. I doubt it's a damaged head gasket. The piston got hot enough to seize in the bore, that's what locked the engine . If your engine has any fore and aft angle to it, the bore at the highest elevation is the one that locked the engine down. My guess is the piston rings are welded to the piston or simply the rings are broken. The continued running of the engine is destroying the bore and the block will need an oversized bore and new pistons and rings. Be prepared to spend some serious money.

Indeed but the OP never said motor seized. His complaint is "However, now the engine belches white smoke all the time. It doesn’t go away after you run the boat for awhile. So I’m thinking that something happened in the overheat situation, maybe a head gasket or something blew. I really don’t know much about these things."

Leak down test could give you more information. Smoke is either coolant, oil or fuel. Really need more info to tell, like does it use coolant, does it overheat still, does the smoke smell like diesel or rotten apples, or like salty steam.

[Scubaseas]

Originally Posted by Carl-T705

. You don't have to remove anything to remove water from a cylinder, simply turn the engine over in the reverse rotation and the water will be pump out the exhaust valve.

Absolutely correct but I said "One way to diagnose is to put a pressure tester on the coolant reservoir, pump to 14 psi and let sit. Take out injectors or glow plugs. Crank over engine. If coolant/water comes out you have a blown head gasket. " which would tell you what cylinder had fluid in it.

[Ballsnall]

Originally Posted by Goofeyfoot

Is my engine dead?

The engine stopped dead ss a result.

I'd call that a seized engine Scubaseas. So highly probable piston & bores are scored. Do the cylinder compression test, coolant checks, oil analysis etc, then pull the head.
Maybe lucky and get away with a head gasket & cyl hone, but you just don't know till the head comes off.

[Scubaseas]

Originally Posted by Ballsnall

I'd call that a seized engine Scubaseas. So highly probable piston & bores are scored. Do the cylinder compression test, coolant checks, oil analysis etc, then pull the head.
Maybe lucky and get away with a head gasket & cyl hone, but you just don't know till the head comes off.

Missed that sorry but usually the motor will do a lot of knocking before it gets to the point of the pistons seizing in the bores. Ring tension may be shot at that kind of heat.

I agree taking the head off would be wise.

[Ballsnall]

With overheating the engine sezure can happen quite suddenly if the engine is only at idle and the damage may be very minimal, if it happened under load or high speed then pretty much can guarantee some sort of damage.