installed a new impeller, took it out for the 4th, jet ski ran great for about 10 minutes, was going full throttle then i let go of the throttle, rpms went down, when i hit the throttle again it just boggs out and will only rev to 4000rpms. barley made it back to shore! pulled out of water, ran it out of water and still the same scenerio, bought new hotter plugs thinking it would solve the problem, but no such luck. Ordering the manuel for it, so if anyone could help it would be great!

gas filter is empty, had old gas in it when i bought it, went through the gas, put new gas, and then this.

 

Could be a couple of things.
Maybe the temp switch is failed, so e-box thinks its over-temp and is doing the rev limit thing (designed to stop excess temp while you limp back to shore).
Maybe you are only getting fire in 1 jug... bad plug wire (check plugs to see if only 1 is wet.) But they usually rev up pretty good on just 1 jug on the trailer anyway.
Maybe its fuel starvation (empty filter... but they usually don't fill all the way up normally anyway). But again, they usually rev pretty good on the trailer since they don't need much fuel under no load.

 

One more thing....
That ski has twin carbs. maybe one is plugged up (old gas)
Take the flame arrestor (cover) off. Then start it up on the hose. Drip pre-mix gas down each throat. One will just be too rich, and maybe bogg down more. The other one (plugged up) should treat the fresh gas like it was starving, and rev up big time.

 

will give it another try tomorrow, with the suggestions you have gave me, update will be comin, thanks again steve

 

Tried what you told me, didn't solve problem. Flushed system out through the water inlet and found out water is getting into piston.. So taking off head and seeing if a new head gasket would solve problem.