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  1. #1
    Legend in my own mind Sirhc7897's Avatar
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    Fins Damaged Ahead of Prop Question

    So after replacing the wear ring last weekend we went out and rode. First hour of the ride ski was ripping out of the hole. All of a sudden though I had problems. Inititally ski didn't want to rev (as if something was binding the pump up). Worked at that for a while and it finally got back to wanting to rev so I thought it was good. Well all of a sudden I had terrible cavitation out of the hole but once the ski got going it was ripping hard...

    I initially thought I ate the wear ring up but top speed was still right at 70 and r's were still in the 8100-8150 range...

    Pulled the pump today and the wear ring is great, prop has a few dings but nothing even close to major, stator is great, etc...

    However the fins ahead of the prop in the pump tunnel are pretty banged up with two being broken down to sharp points...

    Could this cause the cavitation? Can these be grinded down without consequence? If so what's the easiest way to eliminate them?

    Thanks guys...
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  2. #2
    Top banana's Avatar
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    It has been done(cut the fins out) and no problems someone on this site has done it i cant remember who.It looks like you sucked up a bag....

  3. #3
    Legend in my own mind Sirhc7897's Avatar
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    There was a lot of debri in the river so there's no telling...

    You try to be careful but it's impossible to avoid everything...

  4. #4
    Resident Jicky Jack Jeff C's Avatar
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    Banana:

    That would be me. My fins were almost all screwed up in one way or another. Some were almost completely gone. I had a really bad cavitation problem as well.


    I ended up filing those "shark teeth" completely off, flush with the edge.

    I have had zero issues since, with cavitation.

    My only alternative would have been replacement, and the cost of that seemed like it would have been ugly.

    I had nothing to lose, so i tried it, and everything is just fine.......

  5. #5
    Vern's Avatar
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    Bizarre ... Why did SD put them there in the first place?? What was their supposed purpose?? Why would some broken ones cause cavitation (we have heard that before) and why would completely eliminating them seem to fix things and have no apparent effect on anything?? Strange ... wish we knew more about these ... no other ski that I know of has anything like this.

  6. #6
    That last pic look at the shaft going in, Whats white around there? is that plastic?

  7. #7
    Quote Originally Posted by Sirhc7897
    There was a lot of debri in the river so there's no telling...

    You try to be careful but it's impossible to avoid everything...
    I wouldn't be riding in that river.

  8. #8
    Site Admin MikeTrin's Avatar
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    Quote Originally Posted by peteshauling
    That last pic look at the shaft going in, Whats white around there? is that plastic?

    It does look like there's something around the shaft! rope or a bag??

  9. #9
    Legend in my own mind Sirhc7897's Avatar
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    Nope nothing around the shaft. There are a few rust spots on it (I think the guy I bought it from understood that you have to flush the motor after a salt water ride but didn't grasp the concept that you needed to rinse everyhting else down also...).

    That "white" you are seeing is just the flash off the camera...


    So anyways...I filed them down and took it out to the lake to test this afternoon. Zero cavitation and zero performance loss...As a matter of fact...my up-river/down-river average with the GPS in the top storage at the river last weekend was 69.8...this was with the trim neutral...

    Went out today with it mounted proper on the UMI steering and my average was 70.0...I sat ans watched the GPS bounce between 69.8 and 70.3 the whole time with a 1/3 to 1/2 a tank and the trim 2 bars from the top...

    Certainly appears to be no consequences to removing them...

  10. #10
    I have heard that removal of the fins can cost as much as 100rpm's loss so I just put a new one in it is a job but not to much $.If you look at the fins they are angled to start the water spinning before it goes in the pump that is why the say you lose rpm's but you may not lose speed though.

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