Seadoo Challenger 250 mercury optimax dies and makes knocking noise

[Nathanangela80]

I need help.. took the 2003 challenger 250 optimax out today and it ran ok but either has a slight miss or the jet drive wasn't acting right but something was off.. anyway it ran ok for 30 minutes or so then acted like the pistons seized up killing the motor.. after a few minutes it started and sounded like it was knocking and did the same thing at half throttle. I tried to turn it over by hand but couldn't turn the flywheel so I started it again and idled it to the boat ramp and it was still knocking. Later I checked the air pump and fuel pressure and both are good. Could the jet drive get hot and make noise and seize up? Started it a couple hours later and it sounds ok again but still has a miss. I will pull the plugs tomorrow.

 

[Acard7]

Wonder if something was slightly stuck in the impeller causing the knock and when you pulled it out of the water it fell out on the way home. Your miss sounds like a spark plug/ignition coil problem (if it has coil packs).

 

[Nathanangela80]

I'm thinking it could be the bearing in the jet drive seizing up? I filled the wrong side last month so there isn't much oil in it

 

[Acard7]

If it’s anything like the Yamahas the bearing should be sealed and if you grease it you’re just greasing the seal around it.. I would think if it or something seized up on you you’d have some sort of catastrophic failure whether it be the drive shaft or the pistons and it definitely wouldn’t start and sound fine again, but I’m also not familiar with the challengers.. You should pull the pump to inspect it all too when you get to it