jet boat rpm but little thrust

[actionjackson]

89 funjet w/ 90 hp yamaha (dd90) picked up stones rattled with rpms but no thrust, we turned the motor off and trolled for a mile and then fired it up and it was working fine. is there a shear pin on the impeller, or is it direct drive? What would cause this to happen? any help on this particular boat and maybe schematics of the drive would be of great assistance.

 

[thumpar]

Re: jet boat rpm but little thrust

Sounds like you had a rock stuck in the impeller and it decided to come out. I had the same thing happen on my ski last weekend. It would go fine till about 2500rpm and then just vibrate and not really go. I pried the rock out and all it fine now.