Mysterious cavitation!?

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Shane0524

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I have a 1996 GTX. It started to cavitate a little during a standstill hole shot. So I figured it was time to pull the pump. I pulled the pump and found the wear ring in pretty decent shape but the prop was quite chewed. It had a bent blade some good dents and a lot of leading edge damage. I replaced the wear ring and sent the impeller to Dave at Impros. The prop came out great and I was excited to test out the new parts. Shockingly the cavitation is much worse than before with a new ring and new impeller. How is this possible? The only other things I can find are the ride plate/shoe seal and the carbon ring seal. Is there anything else that can cause cavitation? Is there anyway to rig the carbon ring closed to test in for a short term, and any way to test for ride plate leaks? Can someone explain how having a bad plate seal creates cavitation? I just don't get how the plate really has anything to do with the pump flow? I heard you can put zip ties or grease on the carbon ring to temporarily test it? Could I temporarily put hot glue around the plate to seal it and see if it makes a difference?

The one other thing which my be my own fault - I have run this machine alot out of the water recently to test some carb tuning I have done..... I probably ran it for upwards of 5 minutes at a time with no water to the carbon ring. How likely is it that I burnt up my ring seal and stainless plate?

thanks in advance
 
Did you replace the carbon seal and bellows when you replaced the wear ring? A weak bellows will allow the carbon seal to be pulled away from the stainless collar allowing air bubbles into the pump.
The carbon seal also needs to seat squarely against the stainless collar or the same thing can happen.

One more thing:
Did you replace the neoprene seal when you changed the wear ring? If not replaced, this will allow air bubbles in, as well.
 
I did not do anything with the carbon ring or bellows...... it is sealing squarely, i really do not know if the bellows is pushing up hard enough or not. I can easily move the ring back from the SS collar. I did also add a neoprene ring, as there was not on installed previously. any way to test the carbon ring?
 
Look at the carbon seal and se if it is scored up.

I know the wear ring is new, but what does the gap look like. They are not all created equal.


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The wear ring is good, it was an oem seadoo part and fits with very tight clearance.......I really cant see the surface of the carbon ring but it does look shiny on the part that contacts the SS collar
 
Either there's an air leak somewhere or there's too much impeller gap. How much gap is there between the impeller and wear ring? I guess 0.020" should be plenty tight.

Slipping worn splines might be another cause of poor acceleration so consider that possibility?
 
Slipping worn splines might be another cause of poor acceleration so consider that possibility?

Good point on the splines... The fact you had it apart, if the rubber ends are not in place it allows the shaft to move. In some cases, it can move far enough to come out of the spline. Also, it is not uncommon for a shaft to simply have bad spline and allow the engine to high rev and the impeller to do very little..
 
Did you replace the neoprene seal on the pump support or was there one not there at all?


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Also, you can seal up the pump shoe with rtv to eliminate any potential issues like I do.



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I really do not think it is the splines.... they looks fine when I had it apart and the Impeller splines seemed fine too. I just got it back from Impros... the clearance in the ring seems good to me as well. here are some pic i just took, and some from back when it was apart.

I did add a neoprene seal as well.

i'm having a second issue which i think is totally seperate but maybe its not..... rectifier maybe?
 
Did you replace the carbon seal and bellows when you replaced the wear ring? A weak bellows will allow the carbon seal to be pulled away from the stainless collar allowing air bubbles into the pump.
The carbon seal also needs to seat squarely against the stainless collar or the same thing can happen.

One more thing:
Did you replace the neoprene seal when you changed the wear ring? If not replaced, this will allow air bubbles in, as well.

MY 1996 Cavitated a few times Sunday and I think it is pulling the bellows back as jhjesse said wait a minute let off the throttle and it quits I was in silty water both times with leafy dirty debris could have been that but leaning towards a weak rubber bellows. my carbon seal looks perfect.
 
I replied in your other post. Having multiple post in the same issue fragments the replies and makes it hard for others to follow.


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Yes, remember these electronics are decades old on some skis. Erratic solder joints, temperature changes, vibration, different conditions can cause different issues. Its literally a 10 minute job to change the rectifier on your ski. It needs to be changed also as you have that higher than normal spec voltage at battery while running. All final testing needs to be done in water with load on ski. I am not a fan of hoses on skis on trailer testing. Not good for ski, and not what hose connection was designed for. Hose connection is for flushing ski, water flows in opposite direction to rid system of sediments/debris after riding.

Disconnect red wire, and go to lake, or just change rectifier while you are in there and let us know results :thumbsup:

Rob



now i can't get it to replicate the rectifier issue? can the rectifier be intermittent ?
 
Like Joe said, one thread on your ski is all you need. One thread will cut down on confusion.



Rob
 
So back to the original thread....... I'm pretty sure I burnt up my carbon ring. Is there anyway to test it in the water? Cable ties around bellows?
 
On the trailer at the ramp. Fire it up, if water comes in, it needs serviced and or modify the bellows.

Multiple threads are fine as long as it is different issues. Same issues make it challenging to manage.
 
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I had the ski out on Friday an the cavitation is still there. I greased the pto and put some zip ties tightly around the creases in the boot on the carbon ring seal, hoping that would tighten it up, but it did not do make a difference, maybe just slightly better. Is there anything else that could cause cavitation, when has a new wear ring and a new impros prop?

Check out these videos and tell me what you think... am I crazy or is this an acceptable level of hole shot cavitation? https://www.youtube.com/playlist?list=PLTlkdGibArx1ThEycY7SL8TZO9Tj7xJJ0

you can hear how it revs way out to about 7000 and then drops to right about 6800 where it should be, and then really takes off. When i did the were ring and impeller i added a neoprene seal, i remembered that the seal edge stuck down slightly in to the flow of the pump. I removed it and the cavitation seemed slightly slightly better and it seemed faster, possibly just in my head tho....
 
I know the wear ring and impeller are new, but how big is the gap?

If the gap is good and the cavitation isn't from the carbon seal then you likely have bad drive shaft splines.


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How else could i test the carbon seal? I dont know if the zip ties were really that great for a test? I dosent leak when sitting in water with engine off but it dribbles with engine running. Is that normal? Also last time i had the pump off splines looked fine, im pretty sure they would have look ate up if it was spinning...
 
A dribble is normally fine. The water you are riding in is what cools and lubricates the Carbon Seal. So a DRIP is what you are after. If it is more than an occasional drip, then it is likely sucking air..
 
honestly I'm not entirely sure how it was in water when running, but I'm pretty sure it was more than a few drops. I think it was more of a steady dribble. I need to check that again though. Is there any other ways of testing the seal? I have heard putting heavy grease on it?
 
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