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Thread: cavitation.com

  1. #1
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    cavitation.com

    well I'm a bit stumped, maybe somebody will have something brilliant to contribute.

    we get quite a bit of gravel in the pump problems out here. I've done several dozen wear ring/prop refurbs..never a problem..even had o swap out some pump assemblies things got so bad.

    I have an supercharged 4-tec back here with a complaint of no thrust/heavy cavitation..the pump shoe vanes are trashed, but the vanes in the pump are fine. No complaints before the rock ingestion incident, so the carbon ring isn't really suspect.

    In the test tank it hooks up just fine till about 5krpm, then it starts cavitating and if I hold it for more then a few seconds I get an engine overheat alarm ( no doubt it's cavitation, it's not pumping water into the exhaust)

    OK, so I pull the pump expecting to find out I screwed something up, but it all looks perfect..well to a point, I'm not expecting swiss watch precision in there and I suspect when SBT redid the prop, something went wrong. There is .001 additonal clearence on three of the 4 blades, but the wear ring is brandy new and the pump is putting out just fine till 5k.

    I suspect in the tank it's not able to scoop enough water to stay hooked up, but I can't take this ski out on the lake as my new insurance policy doesn't have on lake water tests.

    As I said, I've done quite a few of these and no problem. The trim on this ski was stuck in the full nose up position when it came in, the VTS fuse was blown..but that shouldn't make for this kind of complaint.

    The customers are fun loving types so I don't suspect they are too technical when it comes to describing the issue.

    I'm wondering if the tank test is a red herring and with three people on board and the trim in full nose up if the pump could have trouble hooking up.

    The claimed the ski wouldn't do over 10-15 knts. I can't see how this could be, but the breaking loose in the tank is a bit worrisome.

    Now mind you, I haven't had anything this powerful in the tank until now, so I have no baseline to work from.

    The pump shoe vanes are busted up pretty bad..almost all gone..I don't see this being that large of a problem...am I misguided? Changing the pump mount is something I'm not looking forward to...looks like 4-5 hours of labor and a couple of hundred in parts.

    I'm inclined to put it all together and have them call me when they drag it down to the lake to see what's happening..out here it looks like it should be just fine..no for all I know somebody stuffed a sweatshirt in the air intake ( they called it the "glove box" they tossed the key in there when I wasn't looking and I had a few moments of angst thinking I had dropped the key into the tank) and that was causing the no power problem.

    I'm thinking 3 big riders trim up issue. is the actual "problem" here. Suspect #1

    I'm going to call SBT on monday and ask them if they would send me another prop, Suspect #2 is they set up the machine incorrectly and there is a pitch problem with this prop now.

    As I mentioned, no complaints before this about cavitation, so the carbon ring isn't a really big suspect for suspect #3, but possible. Neither is the neoprene seal..seems to be in fine shape.

    Oh yeah, they are expecting this to be done for free.

    so folks...what say you?


  2. #2
    speedskixp's Avatar
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    Busted up pump shoe vanes will cause bad cavitation. Best theing to do is grind them all out completely and smooth out the shoe. Gunna be hard to test in the tank. I could not imagine working on ski's for a living and not being able to truly water test them.

  3. #3
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    I can live with that...

    won't take much effort to smooth out the busted up shoe.

    Water testing around here requires major insurance premiums, it's a state park...need I say more?

    The tank helps me lots...being a one man operation I'm here alot more then I had been during prior seasons and that translated into more income. Lake testing took a half a day minimum and my truck stank like a skunk after a week or two (fresh water). Not to mention helpful onlookers and what nots taking even more time. Add on 16 miles round trips and you can see why I jumped on getting a tank here

    I appreciate your input on this cavitation issue.

    thanks!
    -pete

  4. #4
    2006 Turbo RXP boBO's Avatar
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    What brand wear ring are you using? SBT or OE?

  5. #5
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    ring is an SBT

    clearances are within range, the ring has a gloss finish on it

  6. #6
    2006 Turbo RXP boBO's Avatar
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    Never ever use SBT parts

  7. #7
    idoodou's Avatar
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    some off brand wear rings have been known to spin in the pump housing

  8. #8
    Eric Ocman's Avatar
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    Quote Originally Posted by idoodou View Post
    some off brand wear rings have been known to spin in the pump housing

    Change the ring bro, I think one of our Mods here posted a thread about SBT wear rings having issues.

  9. #9
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by Ocman View Post
    Change the ring bro, I think one of our Mods here posted a thread about SBT wear rings having issues.
    Before I invest $60+ freight on a seadoo oem ring, I need to see some definitive proof. I've been using SBT rings quite a bit, not a problem so far. As I mentioned, clearances look good, and no apparent problem with the ring. Now I've had some WSM rings that were a bit on the tight side both going in ( even with mr.freezer) and on the prop , but a couple of seconds running on a hose shaved them to fit.

    This ring didn't want to start to go in until it met mr. freezer..that's my test for rings when I get em. If the slide right in I know there's a problem

    I've never had a comeback on a pump job until this one, and my money is on the fact that I didn't "blueprint" the tunnel, I left the busted up vanes as they were figuring something was better then noting. right now the plan is to shave it smooth and see what happens when it gets on the lake.

    appreciate all the feedback there guys.

  10. #10
    Eric Ocman's Avatar
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