jet boat rpm but little thrust

[actionjackson]

'88 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.

 

[ref+10]

Re: jet boat rpm but little thrust

1. Shear pin: actually it has a key on the shaft where it mates w/ the impellor.

2. no thrust: Rocks can get picked up and held against the jet foot intake, restricting water intake (= no thrust). Remedy: shut off the motor and allow rocks / debris to fall away, and you're back in bid'ness!

I've also had small rocks and stones that made it thru the intake and impellor but get lodged (sideways) @ jet nozzle. sometimes shutting off motor will allow these stones to settle, then when you fire it back up, out they go!

3. I've also had to pick rocks / debris out of the intake and nozzle by hand. Big screwdriver / pry bar, needle nose and regular plyers very handy tools to carry!

Good luck!