Bad porposing problem on 97 Yamaha GP760 Waverunner

[frozenokie]

Just bought this ride and no matter where I sit, it porposes terribly in the neutral trim position up to the high trim position. The only time I noticed it NOT doing this to badly (but still did it some) was when the water was perfectly smooth and I almost had to lie down on the seat which isn't my preferred position. Sitting toward the front makes it a little better if any at all, and sometimes not.

Never had this problem on other rides, so I'm new to this problem and new to a yamaha ski. The sponsons are adjustable and currently are adjusted all the way down. Would that be my problem? I figured those were just for making the ski nimble and cut sharply versus skidding sideways on turns while having them adjusted up. I have checked for the correct trim alignment of the nozzle and it is spot on according to my shop manual.

I read a couple threads about the ride plate and shimming it or having an extended ride plate. The one on this ski is about an inch or so past the nozzle. Is this a cause? Should I stick some washers underneath the front of the plate?

Thanks -
Frozenokie

 

[rogerwa]

Re: Bad porposing problem on 97 Yamaha GP760 Waverunner

I have one of these myself and it is a common problem. I put a stack of washers under the rear of the plate and it helped a lot. Didn't go away, but helped a lot. I only put three or four under there so I could probably improve. But this is the cheapest and easiest way to improve the ride..

 

[smclear]

Re: Bad porposing problem on 97 Yamaha GP760 Waverunner

I had this exact ski (bought new) and experienced the same thing. Riva Yamaha made trim tabs for the ski (same hull as the gp1200) and after installing them, the porpoising disappeared entirely. Not sure if they still have them but you might want to check into it. They weren't all that expensive.

 

[frozenokie]

Re: Bad porposing problem on 97 Yamaha GP760 Waverunner

Riva Yamaha made trim tabs for the ski (same hull as the gp1200).

Thanks for the tip on shimming the OEM plate with washers, but I'm looking for eliminating all the porposing if possible - I have the perfectionist flaw

So looking into replacing the ride plate, but which is the best performing without loss of speed or stability? After reading articles, it seems to be the Pro-Tec plate. Any opinions or experience on these?

Thanks to both of you that replied

Frozenokie