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  1. #1
    rick xp's Avatar
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    Getting speed out of GPRSHO - I think I am missing something.....

    Hi Guys,

    I have just finished my GPRSHO build and I am having a hard time gettting some speed out of her.

    My specs are.......

    GPR-SHO

    Motor:

    Completely stock apart from Ribbon and Airfilter. AFR is around 11.8 at WOT.

    Spinning a Skatty 15/25 to 7500 RPM. Stock nozzle sizes etc.

    Hull:

    R&D Rideplate
    R&D Extended trim tabs
    R&D twin bar 1200 Grate

    I have set the rideplate up with a 1.2mm washer in the front and it just below the pump shoe and no washers in the rear. Pretty much setup with maximum angle with no signs of bouncing.

    I have tested on water with about 1 ft of chop and it is currently doing 74.1 MPH. I dont want a flat river top speed boat but a good all rounder that can go out to the ocean etc as well.


    Should i be happy with my speeds considering the conditions or is there more in it?


  2. #2
    TuningForkMarine's Avatar
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    What exhaust do you have ? Also Cut the extended trim tabs to stock size. When I did that on my GpR I noticed a 2 mph difference. Oh and run a dedicated line to your inter cooler, it help I hear.

  3. #3
    rick xp's Avatar
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    Exhaust- Couplers with a stainless pipe inside. Shortend waterbox with Riva free flow.

    Yes already running a dedicated water line to the cooler.

    I hear a lot of people saying cut them but do you really lose that much speed? Do you lose some of the handling?

  4. #4
    RXP 260 X Short Course Veteran RXP244's Avatar
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    Hey Rick, I think at that RPM you are right on the button. You would be at 80 at 8000rpm and pushing 90 at closer to 9k. Chuck a little more boost at it, seems like you have enough fuel.

  5. #5
    rick xp's Avatar
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    Hi Mate, Thanks for the feedback.

    Yeah i think there should be more in it i think. I mean a stock FZR is around the 70 mph mark with minimal mods. Has to be more than 4mph faster with a GPR hull.

    I want to get everything sorted before putting more boost in to her.

  6. #6
    RXP 260 X Short Course Veteran RXP244's Avatar
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    We have always said the GPR hull should be good for nearly 8-10mph with the same HP.

  7. #7
    fx160's Avatar
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    With a rough water setup you are about right
    Get a reflash and let it rev
    Then add a low boost wheel
    You will be mid eighties
    With the same fuel economy
    And just as reliable

  8. #8
    TuningForkMarine's Avatar
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    also mate, keep in mind you are in australia. several threads with people low on speed, its simply an elevation thing. i know a few dudes who would do mid 80's here in FL, but when they sold the ski to australia, it would barely break 75... i didnt see your location tag in TapAtalk. i would have mentioned this earlier.

  9. #9
    Steve-m31164's Avatar
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    Try spacers at the rear of the plate . I was @ 78 mph 7700 rpm on my conversion .let it rev a bit more man . Have fun

  10. #10
    Steve-m31164's Avatar
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    When you say .. plate below the shoe ..... its not lower than the shoe is it ? I ran my plate so the main part of plate was parallel with the hull .
    When I was playing with the trim . Trim up ski would drag its ass , loose speed and rpm . Trim down , nose down , revs and speed up . But every ski is different ...

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