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  1. #1
    Focker Foggy's Avatar
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    Impeller Pitch Question

    What would be the difference if you change
    the leading edge # only, keeping the trailing edge # same.

    ex: 13/19 VS 14/19

    I have not compared these 2 back to back ,,, yet
    but wondered if it is just a holeshot/cavatation/speed/etc issue


  2. #2
    Quote Originally Posted by Foggy View Post
    What would be the difference if you change
    the leading edge # only, keeping the trailing edge # same.

    ex: 13/19 VS 14/19

    I have not compared these 2 back to back ,,, yet
    but wondered if it is just a holeshot/cavatation/speed/etc issue
    This info I'm giving works when comparing two of the same type of impeller (eg. a solas 13/18 vs a solas 14/19, or a skat 14/19 vs a skat 15/20), and does not work when comparing stock to solas or stock to skat, or solas to skat.

    The first number 13/19, 14/19

    this first number determines the accelearation. A 13 pitch will accelerate harder than a 14 pitch.

    The second number is your peak rpm/speed. A Solas 14/19 will give less speed than a Solas 15/21 (if you make enough power) and also run a lower rpm.

    Other factors that come into this equation if you want to be more specific is blade shape, hub diameter, number of blades, and cone type/size. All of these factors change the impeller's qualities.

  3. #3
    Focker Foggy's Avatar
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    these are solas props for my RXT
    I am on limiter with current 13/18.5 so I ordered
    a new 14/19 from Jerry..
    But, I found a 13/19 that I had purchased last year
    and forgot about it. So I was thinking of trying 13/19 first..

    I've got great acceleration with current 13/18.5 , so
    will I lose some by going with 14/19 ??
    i was unable to pull a 14/19 last year, but somehow I have
    more power this year (little mods added this yr)

  4. #4
    Quote Originally Posted by Foggy View Post
    these are solas props for my RXT
    I am on limiter with current 13/18.5 so I ordered
    a new 14/19 from Jerry..
    But, I found a 13/19 that I had purchased last year
    and forgot about it. So I was thinking of trying 13/19 first..

    I've got great acceleration with current 13/18.5 , so
    will I lose some by going with 14/19 ??
    i was unable to pull a 14/19 last year, but somehow I have
    more power this year (little mods added this yr)
    Yes, you would losea little acceleration with the 14/19.

  5. #5
    Focker Foggy's Avatar
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    So then, what is the advantage of ever having
    the 1st # (leading edge) high.. Like the 15/?? that
    guys are running with the X boats..
    Wouldn't a 13/20 or 14/22 give better accell?

    OR is it that IF you have enough power, you should
    always run the largest number possible (on leading edge).

    I know trailing edge is how we tune WOT max rpm's.. Just
    trying to wrap my head around the leading edge numbers..
    Maybe like gear ratio vs. stall vs. trans ratios or something

  6. #6
    Quote Originally Posted by Foggy View Post
    So then, what is the advantage of ever having
    the 1st # (leading edge) high.. Like the 15/?? that
    guys are running with the X boats..
    Wouldn't a 13/20 or 14/22 give better accell?

    OR is it that IF you have enough power, you should
    always run the largest number possible (on leading edge).

    I know trailing edge is how we tune WOT max rpm's.. Just
    trying to wrap my head around the leading edge numbers..
    Maybe like gear ratio vs. stall vs. trans ratios or something
    Well it's just like a car and rear end gear ratios. Too much power with a high number will overpower the prop (and in a car with too much power a high gear will cause wheel spin).

  7. #7
    I have a stock RXT-X (255HP...or so they say). I am more interested in quicker acceleration than I am in bettering the current 68.5mph top end. I am thinking about repitching my stock prop myself as I am only hitting about 8000 rpm. Is increasing the leading edge pitch by .5 mm or so to give it more bite while decreasing the trailing edge pitch by 2mm or so to reach 8150 rpm going to give me better holeshot as well as increase my top end rpm resulting in at the worst, the same top end mph? From what I have been reading, the more power your ski has, the steeper the leading edge it can handle. Am I understanding this correctly?

  8. #8

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    I think you can tune the leading edge, 13, 14, 15, by looking at the tach on a WOT take off from a dead stop. If you spin the prop up and then RPMS drop down you could probably up the leading edge some...

    Ideally I think you want the RPM to go up just past what your RPMS are at top speed and drop back down to top speed RPM quickly..

    If you don't reach top speed RPM on a WOT dead stop take off you should be able to feel the boat struggling and that would indicate too much leading edge...

    What the "over top speed RPM" number on take off you are looking for is what I don't know... might be 50-100 or 100-200????

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