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Thread: need some help

  1. #1

    need some help

    First things first, this is my first post and my first time working on a watercraft, but, I have an automotive back ground so I hope my experience will help me with this project.

    Here's the trouble, I was given my parents 95 slt 750 that seems to cavitate when towing a couple of people on a tube. So the first place I went was the impeller. The manual that I have tells me that the desired clearance between the impeller and wear ring should be between .05 to .20 and a max. wear limit of .50

    The biggest clearance that I have is .55. It also seems that the wear ring is oval. Could this amount of wear cause cavatation? And if so, seeing as a have to replace the wear ring as well as the impeller, can I purchase an impeller with a better pitch for towing?

    Also, I need help understanding the pitch numbers???

    I hope you can help!

    Oh and one more thing. Seeing as it was a 95 and it had a hard life, with NO maintenance, I decided to do a compression test. I couldn’t believe my eyes. It still has 115psi in EACH cylinder haha just thought I would add that for fun.


    Thanks everyone


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk.

    Not sure what book you're looking at, but 20 thousandths is the MAX limit.

    If you have 55 thou, that's you're problem.

    A Skat Trak 12/17 would be a great towing impeller for you.

    Pitch numbers vary between manufacturers.

    Generally the first number is for take off, with the second being for top speed.

    Lower numbers are for a more agressive take off, and good for low HP enignes.

    The higher the second number, the more load is put on the engine and requires more HP to run it without lugging the engine and causing damage. Ultimately the higher the number, the more top speed you'll get.

    For example: Your SLT 750 has 80 HP and carries up to 3 people. (heavy load) So a 12/17 is a great impeller for pulling that much weight, and because you have somewhat lower HP.

    A SLT 780 makes 92 HP and can run a 13/18 with no problem, carrying the same weight, and running slightly faster top speed.

    Now a SLX 780 2 seater still makes 92 HP, but carries less weight can turn a 15/20 impeller.


    The odd ball exception to the rule is the PRO 785. It runs a 12/17 impeller and makes 135 HP. The reason for the smaller impeller is to keep the RPM high. The bigger the number, the steeper the pitch, the more load on the engine, the lower the max RPM will be.

    Hope this helps.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by sim View Post
    ...seeing as I have to replace the wear ring as well as the impeller...
    Welcome to the Hulk

    SBT has an impeller repair service that is quite inexpensive.
    Stainless Steel impellers only.

    I have not used them for impeller repair/refurb, and we haven't heard much from others, but you might want to give it a try.

    You can get good used wear rings and impellers from several sources, including John Zigler.

  4. #4
    casey67's Avatar
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    Quote Originally Posted by sim View Post

    Also, I need help understanding the pitch numbers???

    You are not alone with this confusion

    Welcome to Green Hulk!
    I agree with Xlint,stick with the Scat Trak,and his recommedation's are
    right on

    My friend had a couple impellers fixed by SBT and said they did good work. In my opinion they are probably a good company to fix imp's,not much more than that.

  5. #5
    Bing-A-Ding-Ding-Ding, Brrrrrap! Brrrrrrrrrap!!! Polaris_Nut#1's Avatar
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    Quote Originally Posted by xlint89 View Post
    Welcome to the Hulk.

    Not sure what book you're looking at, but 20 thousandths is the MAX limit.

    If you have 55 thou, that's you're problem.

    A Skat Trak 12/17 would be a great towing impeller for you.

    Pitch numbers vary between manufacturers.

    Generally the first number is for take off, with the second being for top speed.

    Lower numbers are for a more agressive take off, and good for low HP enignes.

    The higher the second number, the more load is put on the engine and requires more HP to run it without lugging the engine and causing damage. Ultimately the higher the number, the more top speed you'll get.

    For example: Your SLT 750 has 80 HP and carries up to 3 people. (heavy load) So a 12/17 is a great impeller for pulling that much weight, and because you have somewhat lower HP.

    A SLT 780 makes 92 HP and can run a 13/18 with no problem, carrying the same weight, and running slightly faster top speed.

    Now a SLX 780 2 seater still makes 92 HP, but carries less weight can turn a 15/20 impeller.


    The odd ball exception to the rule is the PRO 785. It runs a 12/17 impeller and makes 135 HP. The reason for the smaller impeller is to keep the RPM high. The bigger the number, the steeper the pitch, the more load on the engine, the lower the max RPM will be.

    Hope this helps.
    Dare I say a Most Excellent explanation!

  6. #6
    Do you guys have any idea what the stock impeller's pitch would be, just so I can compare numbers with the skat trac impeller pitch you gave me?

    Also, I just wanted to clarify that the tolerances I gave you are in mm and not inch. Sorry about that, I should have added that piece of valuable information. Now that we are clear, are the tolerances from my book acurate?


    Thanks everyone

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    The stock impeller is a 4 blade design, and the book simply says "progressive" pitch.

    Go to Skat Trak's web site and see what they recommend for your ski with the mods you may have done.

    Since you're using metric, .05-.20mm is recommended.

    .5mm is the service limit

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