wear out

I just bought a 2004 Seadoo 4-Tec sportster. Had it out 4 times. The second time, it would rev high, but only go 10 mph. Got it out of the water, filled it up with gas and some seafoam, went back to the lake, and it worked fine. Worked fine the 3rd time out. 4th time, worked fine most of the...