Hi, my name is Rick and I'm new to this forum. I have a similar issue as the guy with the 2002 jet ski. The engine will run fine for the first 5 to 10 min then it will sputter. If I drive it at half throttle it runs just fine. If I hold the throttle open the ski will sputter then work then sputter again on and off. I can sometimes ride it for 20 to 30 min without a problem. It comes and goes. I don't really know where to start. I don't think the problem is the carb or old gas because the problem is intermittent. The ski starts up with no problem. I am just thinking about taking it to the dealership, however, I know this will cost me an arm and a leg. Any advice would be helpful.

 

Does it seem to only happen when the engine is hot, then work fine again when it cools off? If its not fuel related, it could be a problem in the ignition system. A bad coil wont work properly when it gets hot and you will lose spark, try testing the coil/pickups. The procedure is in your manual somewhere, sorry I cant help more. Welcome to KF!

 

Yes it appears to happen when the engine is hot. I will try testing the coil/pickups as you mentioned. I will post with results later. Thanks for your help.

 

If you have not been to the 2002 STS link since your post you might find some new input from these folks in there.

My problem was a bit different in that it didn't sputter at all...it just flat out went from fast to dead. This was more than likely due to the piston heating up to the point where it just stopped the engine in its tracks. Once the piston eroded completely away on the side (picture on the link) it freed it up so that I simply lost all compression in that cylinder dropping my top speed by about 1/3 for the loss of the 3rd (middle) piston. I would say I find this more interesting than frustrating at the moment but maybe that is because we still have a boat to get around on.

For what it is worth...they are very easy to break down using only common tools like a socket set with an extension, a couple screw drivers and a razor knife to cut any lines as necessary. Of course I don't have much $$ invested so I don't mind if I jack things up while I'm learning either. ha!

Good luck!