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Discussion Starter #1
This is the last of 3 problems on this jet ski.

When starting with wide open throttle, it is just about to plane (about 15-17 MPH) when the motor suddenly revs up and acceleration stops. In order to accelerate past this point, I have to back off on the throttle and when it "catches" again I can gradually accelerate. Once past about 22 MPH, the throttle can be wide open with no issue. If I didn't know better, I would guess that it is cavitating causing the motor to rev and killing the acceleration. I have tried all settings of trim but that doesn't help the problem.

Anyone seen this or know what the cause/fix might be?
 

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You are correct it is cavitation. You'll need to check your clearance between the impeller and wear ring. Clearance should be .014"/.018". The max clearance is .024", but cavitation will be an issue if beyond .018". Impeller damage can also cause cavitation. It also could be an air leak around the pump shoe. (The part that bolts on behind the intake grate) they make a seal kit for it that fills all the air gaps in the shoe that help create the cavitation. Riva racing caries them I believe along with others. The shoe can be removed and sealed with a good silicone caulk. With the seal kit, caulk where green is indicated in the pics. Without seal kit, seal where red is. The shoe in pic has a seal kit installed. Just rubber plugs that fill the voids in the shoe. Can also be done with tubes of caulk.

If the impeller clearance is high and you still have the original stainless wear ring just replace the impeller. Then check clearance. Most times the rings don't need replacement. The Solas Concord are a good replacement Impeller. If it has an aftermarket plastic ring. Replace the wear ring insert also. Would suggest going back to original ring from plastic though as they create problems. And need frequent replacement.
Impro's is a good source for Impellers
Find a good used ring if needed on eBay or buy new at Babbittsonline.

Hope this helps, Dave
 

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Discussion Starter #3
This machine sat unused for 14 years and only has 208 hours on it. I will assume for the moment that it is not impeller wear. It also had a ton of ants living inside the jet area. Your advice on sealing the shoe seems like a good and inexpensive first step. As always, I will let you know what happens.
 

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Yes, agree shoe is most likely culprit for air intrusion. Best to check clearance while grate and shoe are off. Will be very easy to get to them.
208hr can still be worn depending on riding conditions.
If you want I have a factory Impeller with 20hrs on it. Slightly lower pitch though. Shouldn't even notice it. Yours is listed at 13.4 pitch mine from an 02 gp800r is 13.2. give a bit more out of the hole and a tick lower top speed. But probably not even noticable. I'll let it go cheep. I'll never go back to it.
 

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I'll check the clearance and let you know. How cheap is cheap?
How's the cost of shipping. I've got no way to measure it or guaranty it will tighten up your clearance. I only know the ski it came off is all original and a 22hr ski when I purchased it 2 yrs ago. It is very clean and no damage so it should be fine. Because of where I ride, and for reliability. I tore the whole ski down and resealed and upgraded some stuff and that included the Impeller. Otherwise it's all original/stock ski. I am at times 3 to 4 miles off shore. Didn't want to leave anything to chance.
 

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Discussion Starter #7
The clearance on the impeller looks like about .014 and the SS ring is spotless. Don't think that is an issue. There is no seal anywhere on the shoe an I'm guessing that's where the air is getting sucked in. I'm going to fill the shoe cavity with RTV and seal around the edges. Ill let you know if that fixes the cavitation.
 

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Clearance is good. So sealing the shoe should do it. There's a foam seal along the back edge that falls out/goes bad and breaks the seal. This allows air in from the ride plate area.
I'll test my gpr's draw this weekend to see if and how much the meter draws. Just for shits and giggles.
 

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Discussion Starter #9
Yes, the foam seal at the bottom is brittle and chunks are missing. I scraped it off and will replace it with a 3D printed seal made of TPU. TPU is a rubbery type material and I will add RTV to both sides as well. I have the shoe pockets filled with RTV now and I will put more around the edges when I reinstall it. That should take care of any air leaks.
 

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Once again, try these two things before you go hog wild.

1. Install an aftermarket Aquavein intake grate.

2. Stuff the pump shoe housing with a pump shoe housing stuff kit.

You can do these two things yourself, and you will need the grate, the kit and some 3M sealer. I did this to my 2001 XLT 1200 which was exhibiting the same characteristics that you describe, and the problem was rectified. A heck of a lot easier than messing with the impeller.

I, of course, eventually changed the impeller but that had more to do with speed than with cavitation. costs were about $100 for the intake grate, $80 for the shoe stuffing and $15 for the 3M marine sealer.

Give it a try before you mess with the impeller. It may save you a lot of time and headache.

Zardoz
 

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posted an update

Dave, i posted a "what's been happening" post earlier today. I am positive you will get a chuckle.

Z
 

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Discussion Starter #13
I filled the shoe with rtv and put rtv around the mating edges. I also mad a 3D printed strip to replace the crumbled strip at the bottom of the shoe and put RTV on both sides. So far, cost is about $9 for the RTV. With any luck, I get to try it this morning.

On the carburetor issue, I decided it was not worth the effort to take the carburetors off again to back out the high speed screws. At 72 years old, I don't need to have the fastest Waverunner around.
I'll let you know how it goes later today.
 

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Discussion Starter #14
The RTV in the shoe has solved the cavitation problem completely. It's a great $9 fix. I can accelerate full throttle from an idle and it does nothing but accelerate time and time again. Thank you so much for the RTV tip.

This Jetski is acting like new with the single exception that it surges a little bit at the top end. I am happy.
 

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Hello, i am new to this forum, so not sure how to ask a question or start a thread but it is related to Yamaha 2001 XL800 battery issues also. I get a battery alarm beeping and flashing in the gauges, if i charge the battery then it will go sometime ok but then the alarm comes in. The battery has 12v with ski off and also just 12v with ski running.
is it the rectifier/regulator, how do i check before i spend the money and buy it. The fact that the voltage is not increasing when the ski is running tells me that the battery is not charging, am i correct? any ideas are welcome.
I hope i am imposing by adding to this thread, thanks
 
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