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  1. #1

    Join Date
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    03 GTX SC Riva Stage one slower

    Hi, I am new to the board and just purchased an 03 GTX SC watercraft. On my first day of riding, I noticed that the ski would cavitate badly upon acceleration, but once going had some good power and rpm's were around 7450 give or take. I went and purchased a Riva stage one kit for it along with a new wear ring. On my next outing, the cavitation was gone but it felt like a dog. The acceleration was worse and the rpm's wer only 7050. Althought top speed on the speedo was about 4-5 mph better. I then tried the original impeller and the cavitation came back, but the rpm's read 7630. The speed went down about three mph, but the boat felt a little faster. I called the Riva tech line and they told me to check the SC clutch clearance, that it was highly unlikely their impeller was wrong. My questions are, is it possible that the impeller they sent me is pitched wrong, and is it possible that my stock impeller is worn out, because when I even give it half throttle from a start it feels like the motor is just spinning. I am sorry for the long run on paragraph, but any help anyone can offer would be highly appreciated. Thanks, Rob


  2. #2
    Site Admin Green Hulk's Avatar
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    Check your pump seal!

  3. #3

    Join Date
    Jun 2007
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    South Jersey
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    Is that the big black O-ring that goes around the front of the pump where the wear ring sits? Thanks for the response.

  4. #4
    lextoy's Avatar
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    your old prop is probably damages and cavitiating, send it in to be refinished back to OEM specs, and keep it as a spare and a swap to ge teh new mods dialed in.
    i think your new prop needs to be tweeked, if it is reading faster speeds but is a dog out of the hole, and isnt getting full rpms then its not pitched perfect.
    is the new prop pulling hard out fo the hole, zero cavitation, or is it cavitiating badly also??
    what pitch is your stock prop??
    what pitch is the new prop??
    get that stocker refinished and tweeked and it might be your best all around prop. it is running closest to the 7600rpms you need.

  5. #5

    Join Date
    Jun 2007
    Location
    South Jersey
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    23
    The stock prop is whatever comes stock. The aftermarket one is the Solas / RIVA Concord Impeller SR-CD-13/20R. I have heard these impellers can rob more than 400 rpm's if not pitched right. Riva is saying it is more than likely not the impeller but it is the supercharger. The ski pulls to 7630 rpm's with the stock prop in it, so is it possible it is the supercharger? Also, with the new impeller, it doesn't cavitate out of the hole, but it is just sluggish. I am thinking my stock impeller is shot and needs reconditioning and the new one is not pitched right. Any thoughts? Thanks again.

  6. #6

    Join Date
    May 2005
    Location
    Louisville KY.
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    156
    The 13/20 will lower your rpms about 300. What shape is your wear ring in?

  7. #7
    Mentally Unstable dochere195's Avatar
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    Jun 2007
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    It's the 13/20r impeller. Repitch for optimal performance. A 12/20 would suit you better with a stage 1. Send to Island or Impros to have it done right...

  8. #8

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    Jun 2007
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    The wear ring is brand new. Why would Riva claim higher rpm's with this impeller? Anyway, do you think the supercharger is ok with the rpm's the ski puts out with the stock impeller? Thanks again.

  9. #9
    NCNismo32's Avatar
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    Jan 2007
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    1. SC Probs will see you turning 6500 and lower RPM's you won't see 7K
    2. High air temps kill the amount of RPM's you will see w/ this ski maybe more enhance w/ a Stage 1 assuming you have the Air Intake on it? Mine lost about 80-90 RPM's in 92-93 degree heat last time out.
    3. Ask Pale Rider on questions regarding the GTX SC, he knows it better than most.
    4. I got the Skat Trac 16/21 although Glenn has a new 3 blade impeller that he will repitch continuously for free for about the same price that he thinks is much better. I bought based on PR's experience w/ the 16/21.
    5. There is probably a reason this guy sold this ski for 6K did you get a compression test done on it yet?
    6. Do the reverse gate trim mod on it to enhance the outflow a little bit.
    7. What is your GPS speed associated w/ the RPM's your turning? 12/20 should bring RPM's down but top end up I think.
    8. Shoulda bought mine.

  10. #10

    Join Date
    Jun 2007
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    South Jersey
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    1. I guess the supercharger is OK.

    2. I will contact Pale Rider. Thanks

    3. I never did a compression check, but the ski runs great with the stock impeller other then off the line. Did I mention how much I paid?

    4. What is the reverse gate trim mod and what does it do for performance?

    5. Never GPS'ed it. Going on rpm's and feel only.

    6. Never knew it was for sale. Thanks for the reply.

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