1999 Seadoo GSX RFI Runs Perfect Highspeed rough idle and dies

[ChrisNashville]

I bought this 1999 Seadoo GSX RFI more than 6 years ago. It sat in a factory indoors in a heated environment.

I took it out last summer filled it full of new fuel and oil.

I dropped it in the water and it ran very very rough. sputtered and smoked then would kick in and run for a minute and start sputtering. Eventually it really smoothed out and I rode it for 8 or 9 minutes wide open. was smooth and ran perfectly. When I got back close to the dock and I slowed down it started running rough and then when I tried to give it throttle it shook and vibrated very bad. Like it was only running on one cylinder when the throttle was more than half way open and would not run on both cylinders.

I turned it off. Let it sit for a while and went back out. Started ok went back out and ran it for 10 minutes or so and it ran perfectly at high speed. But same issue happened when slowing down.

Same scenario 4 or 5 times before I pulled it out of the water.

I got it home. drained the gas. Poured some heat in the tank and filled it up with a few gallons of fresh gas. I will change the spark plugs. What else can or should I do?

Thanks,

 

[mikidymac]

First check compression with a good gauge.
Check voltage at the battery with the engine revved up to about 4,500 rpm. It should be 13.5-14.5 volts, above that or below and the voltage regulator is bad.
Next, you need to pull the fuel sending unit and change both filters, and while it is out drain and clean the inside of the tank.