What the Cavitation?

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The wait was over and a 2003 Sportster Vtec 155HP found its way to my driveway this weekend - and what a weekend to be on the water :hurray:. It was great!

Of course, there's the learning curve of the jetboat - low speed driving will take some getting used to. There was a repair -- what's a weekend without one. And then the cavitation .... or that's what I think it is as haven't experienced it before ... basically high RMP, low speed, and slow to no planing. BTW, what is normal RPM for WOT on this beast?

Boat gets to plane on WOT with about 340lb load in around 7 seconds. OK, but sounds slow.
Boat takes mucho longer with a U-tube behind it approx 15-20 seconds -- I would expect some drag to affect planing, but should it be significant? U-Tube loads were approx 200lb, and 375 in the boat. One load of the U-Tube didn't even allow us to get to plane -- rev'd out 7K but only got to 12-15 on the speedo for an extended period before I backed off.

Does that all sound like standard cavitation stuff and I should be checking my wear ring and impeller -- impeller looks fine to naked eye.
Is there a special gauge to use for the clearance between impeller and ring?

Thanks for input.
I just had that problem last weekend--kinda scary when it revs that high and you're not going anywhere. For me, driving in reverse for a bit while wagging the wheel back and forth eventually spat out a bunch of chopped up weeds. No problems after that. You should be on plane in about a second when you gun it.

Try cleaning out your grate and/or impeller. While asking on this forum though, a lot of people brought up the wear ring too.

Good luck!
Sounds like a plan ... can't see anything from the back that may have got sucked in but will try and take a look from the intake.

Don't see anything immediately visible, but probably worth a closer look.

check condtion of impeller and wear ring while inspecting. If you see damage then good chance thats al least some of the problem. for real good look take the nozzel and gate off. My find something wraped in there also. A few eeeks back I found a piece of life jacket start in there. Removed it and back to normal now.
Yeah that boat should plane in a couple seconds, not 7. You probably have a bad wear ring, possibly an impeller. If its winding up to 7k I kinda doubt something is in the intake. But I have been wrong before ;)
Appears it was both -- wear ring was wore out a bit and there was a sizeable gap between impeller and ring. Also has some gouges and nicks in it.

The impeller was an issue too -- some nicks and one gouge that had bent part of the fin partially over. Wish there was somewhere in Canada that refurbed impellers as the shipping was killer to get SBT to receive mine, and then send me back one (at least theirs is coming in 2 days).

Hopefully all back together Friday for the loctite to set for boating on Saturday. :hurray:

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