Intermittent Thrust Issue

[King908]

Good Afternoon,
I have a Polaris Virage i, getting time to get it ready for the spring, and last season I only had time to get out a few times.

What was odd, was the engine was throttling up properly, but I was not getting the proper amount of thrust based on RPM. If I was under 3000RPM, I never noticed a problem.
The problem was above 3000, trying to get on plane.

If I revved the engine RPM's up and down a bunch of time in the water, eventually the pump thrust finally engaged, and then had no more issues for the rest of the day. But then the next day or week, the same issue occurred.


Since I trust all of your knowledge since helping me get passed my Check Engine light, I hoped that you had some ideas on where I could start my investigation to the issue.
Thanks,
Jonathan

[K447]

Well, start with checking the driveline. Remove the jet pump and inspect the splines on both ends of the drive shaft, and inside the impeller and the engine coupler. Do NOT stick your finger inside the hole, metal splinters are painful. Splines should be square shouldered, not worn or rounded over.

Also check the rubber bonded drive coupler on the rear of the engine for any signs of the rubber bond failing.

While you have the jet pump removed check the impeller bearings for zero slop and no play, no gritty feeling or noise when turning. Also check the impeller blades for damage, stuck debris, etc. Same with the stator vanes.

My signature links include info showing how to remove the jet pump and inspect the impeller.

Keep track of the small rubber end bumpers that are located on each end of the drive shaft. Sometimes they stay in place on the drive shaft, sometimes they end up hiding down inside the impeller or drive coupler.

[BlueFishCrisis]

Good Afternoon,
I have a Polaris Virage i, getting time to get it ready for the spring, and last season I only had time to get out a few times.

What was odd, was the engine was throttling up properly, but I was not getting the proper amount of thrust based on RPM. If I was under 3000RPM, I never noticed a problem.
The problem was above 3000, trying to get on plane.

If I revved the engine RPM's up and down a bunch of time in the water, eventually the pump thrust finally engaged, and then had no more issues for the rest of the day. But then the next day or week, the same issue occurred.


Since I trust all of your knowledge since helping me get passed my Check Engine light, I hoped that you had some ideas on where I could start my investigation to the issue.
Thanks,
Jonathan

I had a similar issue on a different ski. I actually figured out that if I turned while applying throttle it would jump up on plane nicely. Engine would rev up near the limiter when thrust was lost... Played around with it for a few hours trying to figure it out. Finally took it home, pulled the ride plate, and resealed all the crevices where the intake grate and ride plate met the hull, and each other. Somehow, the angle of the ski when taking off was causing some kind of air bubble that was getting sucked into the pump and ventilating it causing a loss of thrust. Once up on plane and settled in, the issue went away.

Once I removed, re-installed, and resealed everything, never had the problem again......