Engine locked up

[GreenGTX787]

I have a 1997 seadoo gtx with the 787 engine. When I bought the pwc it needed a head gasket. Me and a friend who has experience with these engines took the heads off to replace the gaskets and inspect the internals of the engine. The rod bearing were in good shape along with the pistons and sleeves. After putting it all back together we took them to the lake the first day it ran smoothly no issues at all the next day at wide open throttle it locked up. It did not bog or make any noises such as a rattle or knock it just shut off. We pulled the top end to see if it was a piston but both pistons and sleeves were still in grate shape and with no compression we were able to work it back and forth about a half of turn of the crankshaft. Whatever has happened seems to be bottom end but I don’t know enough about these engines to know if it was a rod bearing or crank bearing.

 

[mikidymac]

Your engine only uses o-rings for the head so I assume that is what you are referring to as head gaskets.

I would pull your jet pump first as that might have locked up and not the engine.

If the engine is still locked up after removing the pump but rotates a little bit it could be the brass rotary gear that has stripped.

 

[GreenGTX787]

Thank you I’m gonna do that after work but the gasket I was talking about is the one between the crank case and the cylinder heads

 

[GreenGTX787]

It was spraying water out the front side of the engine

 

[mikidymac]

There is no gasket between the crankcase and cylinder head.

I assume you are talking about the base gasket that's between the cylinders and the cases?

The head does not contact the cases, there are cylinders between them.

 

[IDoSeaDoo]

Might be one of the big crank ball bearings. Probably time to yank the motor :/

 

[GreenGTX787]

Yesterday we pulled the heads and everything is in great shape. Pulled the jet pump and it wasn’t locked up we did notice though that the exhaust did not have water in it nor this the hoses going into the top of the engine. Might have overheated but there is no scoring or burn marks on the piston or cylinder walls like I said that was all still in great shape

 

[mikidymac]

At this point you might as well pull the engine.
1. Pull the engine and get it on the bench.
2. Pull the rotary valve cover and see if the rotary disc is damaged.
3. Split the cases and see what you can find.