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Discussion Starter #1 (Edited)
Help! I have a 2001 Yamaha XL800 three seater (120hp) with 120 hours. Engine runs well but from 8mph to 20mph, the engine will overrev without picking up speed. If it had a clutch, you would say it is slipping. Once I get up to 20 mph or so, it runs fine without slipping. I thought this PWC had a direct drive so how could it be slipping? Could be air in the impeller area. Someone said the wear ring might need replacing but the impeller seems to have little if any clearance with side of housing. Could it be a worn impeller? It has some a few nips. Or something else? Ideas?
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Hey I just experienced the same problem on my 2002 GP800r.. I was cruising around at 30mph and hit a medium sized wake when this first occurred... After about 10 minutes of idling back at 7mph(if i gave it gas it would over rev) finally the problem sort of went away and I got back up to 41 mph before i eventually slowed to 25 and ran into a small wake and the problem came right back.. It would idle fine at 4-8 mph and when I gave it more gas it would start to over rev, so I had to idle the rest of the way back.. I really don't know too much about wave runners but I'm guessing It's something to do with the Pump Seal or the Impeller.. Any suggestions anyone?
 

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Sounds like the seal in the pump shoe has blown out since you say the impeller has minimal clearance and no damage (make sure you check, clearance should be around 2-4thou). Remove the pump shoe (clean it) and sikaflex all areas that connect with the bottom of the ski, including under the pump ring. What is happening to your ski is cavitation. You will have to remove the scoop grate with 4 x 10mm bolts and pump shoe with 4 x 12mm bolts. Make sure when you re-assemble you but the long 10mm bolts to the front of the scoop grate.
 

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Discussion Starter #4
Thank you GCwaverunner

GCwaverunner-you were right on the money. I had gotten similar info from a local PWC mechanic a week ago after I noticed a rubber piece hanging down below the ride plate. I took off the plate on the bottom along with the lower impeller housing. I used an instant gasket material called "The Right Stuff" from NAPA. The tube was pricy ($24) but it did the trick. Evidently, at low speeds no air gets down in the impeller area but when I got it up to about 8 mph, air starting entering from behind the impeller area through the missing rubber seal allowing the impeller to capitvate. The sealant worked.

Thank you. Kitflyr.
 
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