Loss of 500 rpms on top end after wear ring replacement - 96' XP

[1983]

What's up guys?

Question for you all on my 96' XP. Its been running great, pulled 6900 RPMS on the last ride, no issues with how it runs, just cavitating out of the hole due to wear ring completely shot.

So only thing that has changed was what I did saturday:

I replaced wear ring, jet drive oil, and neoprene hull to pump seal. Sealed everything up correctly with RTV to hull around bailer and pump tubes, made sure pump shaft bearing and washer went back to correct placement and everything spins freely. Everything installed to a T. Went to ride it yesterday and it accelerates so much better, pulls better through mid range, and even feels faster on top end. But im only pulling at most 6450 rpms now

Also I installed R+D nozzles setup I had laying around. Could that be restricting RPMs or something? Also, water wasn't like glass out there, but was decent enough to where I should be able to get RPMs like I used to in the higher 6k range.. where did my RPMs go?

Break in period for new wear ring or something?

Rob


Before:

After:

 

[1983]

[MENTION=51824]Matt Braley[/MENTION] any thoughts on this? I know you're the nozzle expert

 

[Matt Braley]

Yes Too much "squeeze". And you changed two things at once. I think the tight tolerance of the new wear ring around the impeller is dropping rpms up to 100 but giving you better all around performance. The nozzle set you have is long and the opening looks small. Those rings in that one are replaceable so that's nice. How many mm is the opening? A stock steering nozzle is like 96mm and from what I've found you can squeeze it down to around 90mm before loosing rpm. Then you start gaining speed if you have the power. 88mm is a sweet spot for the 110hp range. There is a little power left to pick up a mph there in a strong stock engine. After that rpms start to drop without a performance gain. In fact it can stress an engine like a four cylinder car going up a steep hill stuck in fifth gear.

 

[thomps33]

Yup, what Matt said. Was the weather significantly warmer on your last ride?

 

[1983]

I'll measure nozzle mm and repost, caliper was on loan to buddy.

It's odd, ski doesn't cavitate at all anymore. Plus it feels more peppy throughout whole powerband. Plus top speed feels increased. I will gps it this weekend. I could only pull 6450-6500 rpms yesterday. Was 6800-6900 before work was done.

Yes on the last ride with worn/bad wear ring it was hotter and no storms that day.
Yesterday was on and off storms and 10 degrees less temperature.

Just double checked water regulator, it's still good to go. Last year that is where I was losing my rpms at, fixed it and good to go.

Rob

 

[1983]

Thanks for feedback guys,

It is great to feel how these things jump out of the hole like a frog with the fresh wear ring.


Rob

 

[Matt Braley]

The diameter of the exit nozzle is as much or more important as the steering nozzle. You don't want less then 85mm

 

[1983]

K, I will disassemble and measure both exit and steering.

Matt what do you mean by the rings in that one are replaceable? The nozzle ?




Rob

 

[thomps33]

There's a set screw in the end of the nozzles to make the rings removable. You'll be able to interchange them with different size rings to make tuning it easier. I bet your exit and steering nozzles are of the interchangeable type.


Sent from my iPhone using Tapatalk

 

[1983]

I gotcha, I doubled checked those set screws before installing the setup Saturday.

I will check mm and post back.

Rob

 

[1983]

Well I checked the steering nozzle mm real quick before work. It is 87.68mm so I guess you can call that an 88mm steering nozzle. That is ok to use on a stock 96' xp correct?

If the exit nozzle is 85mm I guess I will leave the combo on the ski.




Rob

 

[Matt Braley]

That's normally the ticket. I would gps and rpm check with both those and stock.