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  1. #1
    Vern's Avatar
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    RXP pump mod - 5 vane?

    I can't remember where I read it, but I think Jerry said that Dan (JD1) does some pump mods. I know he sometimes does a set-back mod, but I have also always wondered about the number of vanes. Someone else questioned if some of the speed of the GPRXP setups was due to the Yamaha pump, which only has 5 vanes. I always thought it was due to the hull, not the pump.

    Anyway, what I have always wondered is if anyone has ever cut out every other vane on a stock RXP pump and tested it? Generally more vanes = more takeoff, less cavitation, but less vanes seems to yield higher top speed. Soooo, just wondering .... anyone ever try this?
    Last edited by Vern; 09-12-2007 at 04:46 PM. Reason: mistake


  2. #2
    HORSEPOWER JUNKIE 9secZO6's Avatar
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    I mentioned the possibility of SOME of the speed increase being due to yammi pump design, and was dismissed..."it's all in the hull"...uhh, ok then. Matters not, GPRXP for me, but would like to know.

  3. #3

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    If I remember correctly more viens= better hole shot

  4. #4
    cheatin' piston popper addicted's Avatar
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    Yammi pumps have 6 veins. The speed is from the efficency of the gpr hull. Think of pushing a bathtub through the water, versus a steak knife.

  5. #5
    From what I understand the veins straighten the flow, acting on the rotation of the impeller as in opposite to create thrust/pressure as the water exits the venturi/nozzle, like a torque converter in an auto trans, so the more the better. am I close? yes/no?...PR...

  6. #6
    Quote Originally Posted by addicted View Post
    Yammi pumps have 6 veins. The speed is from the efficency of the gpr hull. Think of pushing a bathtub through the water, versus a steak knife.
    a bathtub eh? ...PR...

  7. #7
    Quote Originally Posted by addicted View Post
    Yammi pumps have 6 veins. The speed is from the efficency of the gpr hull. Think of pushing a bathtub through the water, versus a steak knife.
    There is speed in the pump design. Hull design reduces drag, so there is speed to be had/lost there, but it doesn't transfer HP to the water.

    I'm not saying the GPR pump is super duper efficient and transfers more HP to the water than any other pump, but it is a possibility. Has anyone done tests to check it's efficiency, HP transfer, thrust, etc. versus the RXP pump?

    I have read (not sure if it's true) that the more veins the better the holeshot and hookup, but you see a loss in speed. I'm sure there is an ideal number either way though. There are probably a crap ton of factors that are WAY over my head that affect pump efficiency.

  8. #8
    cheatin' piston popper addicted's Avatar
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    PR, you are right, the veins straighten the flow. The more the merrier to a point, because they also load the pump and motor. A 14 vein pump will slow down a ski, because of the extra load, just like a steeper prop, but improve the hookup and holeshot alot because the veins are stuffing the cavity instead of water.

    I don't know much about the GPR or PXP pumps. That being said, the RXP pump has to have some kind of advantage because they have a killer holeshot. That motor in a gpr hull = boiled water from what I understand from mark and joe.

    Either way, the fact is that jets suck ass as far as efficency goes. I think around 40% is all we can put to the water.

  9. #9
    cheatin' piston popper addicted's Avatar
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    Quote Originally Posted by Pale Rider View Post
    a bathtub eh? ...PR...

    I was trying to be nice

  10. #10
    Quote Originally Posted by addicted View Post
    I was trying to be nice
    Yeah I know , I heard you "all" day long Yami yami yamiha a a a a a, yami yami yamiha a a a a ...PR...

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