96 Speedster wont accelerate.

[GJohnston70]

Morning,
I am new to the PWC world so please bear with me.
Just purchasted a 96 Speedster with twin 717's, did not water test before buying. Anywanys, runs great and fast when it is on top of water. We live on a no-wake zone in the river, have to travel 5-10 minutes up river before we can open it up. I thought it was a little slow to come out of the hole but as soon at it planes it a little rocket. We go for a tour on off the trottle and it works great, come back to the no wake zone down to idle putting along and went to throttle up to get out the way of an other boat and all it does is rev out and go nowhere. As long as we tour along at about 3500rmp it will do 10mph, push the throttle and it just revs and slow down. It has done this 2 days in a row.
Any help would be appreciated, where do I start? Wear rings, impellers, shafts.

 

[Ckrawiec]

Well, if the engines revs up but the boat NO GO, first thing I'd check is the wear ring clearances between the impeller(s) and the wear ring(s). The clearance is supposed to be miniscule (0.10 mm), so as the gap increases, the boat's ability to squeeze the water through there and push the boat forward decreases.

The engines revving up but the boat not increasing in speed is probably causing the engines to hit the REV LIMITER (built-in to the MPEM) and then slowing down.....my best guess at this point.