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  1. #1
    Focker Foggy's Avatar
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    Impeller pitch ??

    OK guys/gals, I understand very basics of the pitch numbers, etc.

    Looking for some kind of comparison/explantion of the
    numbers themselves and how they relate to top speed, acceleration,
    out of hole, etc.

    the larger the number on the pitch = less rpm, more top speed (assuming
    you have the power to turn it)..
    How is the 1st number on pitch compared to , like, gear ratios in a car.

    Does a 14/19 and 15/19 have same top speed, but diff. bottom end??
    Going from a 13/18 to 13/19 would just bring down rpm at top only?? as
    compared to gong from a 13/18 to 14/18 does what??

    These are just numbers I'm throwing out.. iknow specific skis, power combos
    would react diff. in diff situations, But if all else werer equal and
    we added/subtracted from each number, what is result.. Thanks


  2. #2

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    I know for sure that the leading edge effects hole shot and the trailing edge effect top RPMs.

    Pretty sure they each overlap the other... interested to see what others have to say.

  3. #3
    Focker Foggy's Avatar
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    So if my rpms on top were ok and I wanted to get
    a better holeshot then I should change
    my pitch from 13/18.5 to a 14/18.5 ???

    Would this keep my top speed and top rpms the same, but
    just give me a better holeshot

  4. #4
    Sarge707's Avatar
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    Quote Originally Posted by Foggy View Post
    So if my rpms on top were ok and I wanted to get
    a better holeshot then I should change
    my pitch from 13/18.5 to a 14/18.5 ???

    Would this keep my top speed and top rpms the same, but
    just give me a better holeshot
    I,m No Expert but I think the 13/18.5 would give you the better holeshot?
    Others will help I,m sure!

  5. #5
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by Sarge707 View Post
    I,m No Expert but I think the 13/18.5 would give you the better holeshot?
    Others will help I,m sure!
    Foggy, My experience is that the less degrees pitch on leading edge is less prop spin with better holeshot. I don't think going from a 13 to 14 is your answer. What exactly are you looking for? Did you have prop spin, how was your holeshot?

  6. #6

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    Shouldn't there be that fine line with the leading edge. If it's too steep and you pin it from stopped your boat will feel like it's working too hard. Where as if it isn't steep enough you will get prop spin... easy to tell because your RPMS will shoot straight up. It's how long the RPMs stay high before you start to fly that you want to pay attention to... I think?? HAHA...

    These pros will chime in...

  7. #7
    Focker Foggy's Avatar
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    I tried a 14/19 and was a little too tall in the heat anyway..
    then I munched it in rocks.
    So I bought a 13/18 and was on the limiter, but out of the hole was
    pretty good.
    Then I munched it with debri

    I sent both to impros to repair and repitch.
    He did them both similar (I think anyway).
    I put in the 13/18.5 (added pitch to 13/1.
    I'm fairly satisfied with results. Just thought I'd have
    a little more top speed. rpms are 8080 in heat. But at
    end of season, I added the ppg power pipe & deleted resonator
    for shits and grins. I was very close to limiter.. got 8160 pretty
    consistently at 69.x mph.

    From what i've seen with other's mods, I really should be over
    70 mph. I know I could put in an external I/C, but just
    shy on funds now (wife losing job this month-16 yrs+).
    I am getting my rpm's into the sweet spot, just not
    getting the mph I think I should have/want.

    So I though about putting in the other prop. It's a 14/19
    with pitch taken out , so now is 14/18.5.

    Just wondering what net effect would be in my situation, or
    should I just F it for now and wait til I get an ext. i/c and
    then repitch.. it would be summer in the heat at least.

  8. #8
    Focker Foggy's Avatar
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    Steve, I was also "thinking' of the ecm reflash service.
    That would bring my rpms up 100+ or so.
    Would I just use the same impeller that's hitting 8160+ in
    the cooler weather?? would it just keep revving to its' 8300+ ??
    It would end up a little cheaper overall then doing an ext. i/c.

    I just dont want to keep doing the same crap over and over..
    getting pricey !!

    I am for sure going to fill my ride plate holes this month, but i'd
    like to get best bang for buck (if buck available)

  9. #9
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by Foggy View Post
    Steve, I was also "thinking' of the ecm reflash service.
    That would bring my rpms up 100+ or so.
    Would I just use the same impeller that's hitting 8160+ in
    the cooler weather?? would it just keep revving to its' 8300+ ??
    It would end up a little cheaper overall then doing an ext. i/c.
    When you allow for your ski to run more rpms you have to set up your prop based on power but to run the extra rpms. So if you had a prop that was on the limiter that would be a good prop to start with if you were to run more rpm. Then you would take out pitch to bring rpm up.

    I just dont want to keep doing the same crap over and over..
    getting pricey !!

    I here ya, I am taped out on my RXP and refuse to add anymore coin.

    I am for sure going to fill my ride plate holes this month, but i'd
    like to get best bang for buck (if buck available)
    If the engine can handle it, I like the idea of the 8,380 rpm reflash. It would definitely be as good of bang for the buck as an SC upgrade on stock ecu IMO.

  10. #10
    Focker Foggy's Avatar
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    What do you think the net difference between
    a 13/18.5 and a 14/18.5 would be..
    Holeshot, top, mid, etc top rpms, speed ??

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