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  1. #1
    philip_gpr's Avatar
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    SHO (and maybe FZR) pump setback modification - Worth 1.5 mph

    One of the things you can easily do to the SHO is set the pump back an additional 2 inches.

    This can be done using off the shelf parts. You simply add the GPR 2 inch pump extension housing and replace the SHO driveshaft with the 2 inch longer FZR driveshaft on your SHO.

    With my basically stock SHO this resulted in a 1.5 mph gain. I have since confirmed similar gains with a couple of other forum users. Before anybody asks, my testing was back to back, identical conditions, runs within 20 minutes of each other.

    I am also working with using the Seadoo pump on my SHO. When you add a Seadoo pump you have to do some modifications to the Yamaha OEM driveshaft. This allows me to chose any amount of setback I wanted. With my Seadoo pump set-up I went as high as 3 inches of setback. Note - In my case for simplicity I had the reverse bucket removed so with 3 inches we probably should check to see if the reverse bucket stil fits properly.

    I believe the speed gain is a result of increased leverage. The further back the water exit is the more upwards leverage the 5 degree exit nozzle can exert on the hull to get the front end up.
    Last edited by philip_gpr; 04-26-2011 at 09:42 PM.


  2. #2
    SHOBiz's Avatar
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    Good, but that has to rank as one of those higher cost 1.5mph's with a shaft alone costing what around $300?
    eh, maybe that isn't that bad after all...

  3. #3
    philip_gpr's Avatar
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    It is actually pretty good because you can then sell the SHO driveshaft to someone putting together a GPR-SHO.
    Last edited by philip_gpr; 04-26-2011 at 09:42 PM.

  4. #4
    mjh3ides's Avatar
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    I'd thought about trying this awhile back, but the difference between the SHO & FZ shaft is not 2", it's more like 1-1/3". That means after installing a 2" spacer you'll have 2/3" less spline in the midshaft which made me hesitant to do it for fear of stripping a driveshaft or midshaft or both, especially on skis making big power.

  5. #5
    philip_gpr's Avatar
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    So I just checked and it looks like the FZR driveshaft is 30 5/16 inches long.

    The SHO drivesahft is 1 7/16 inches shorter. (sorry my mistake) So there would be 9/16 in less spline engagement.

    The total length of the splines is 2 1/2 inches

    I have used this set-up on a stock ski and also with a C3 wheel with no issues. I think one of the other forum members I spoke with was using it with a B1.

    The OEM driveshaft is very high quality material. I am not sure what the maximum boost (hp) that this set-up would support is. We know with C3 or B1 it is fine. I will trying it again this summer with a much larger wheel.

  6. #6
    mjh3ides's Avatar
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    Keep us posted on how it holds up. Was there a noticeable difference in handling?

  7. #7
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    yes this mod works as i have done to my SHO. I only had a 1 mph gain . I used a gpr 2 inch spacer and FZR shaft the only problem, I had was the adapter was 2 inches to short to hook up the sterring and trim other then that ,a easy way to be faster then the next guy --also it feels like u are hook solid to the water.

  8. #8
    hitman's Avatar
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    Could you have the GPR 2" extension machined so it's not quite a full 2" extension?

    I like this idea, just wondering how setting back the pump effects hole shot and low end cavitation.

  9. #9
    dhoad's Avatar
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    Quote Originally Posted by Big brother View Post
    yes this mod works as i have done to my SHO. I only had a 1 mph gain . I used a gpr 2 inch spacer and FZR shaft the only problem, I had was the adapter was 2 inches to short to hook up the sterring and trim other then that ,a easy way to be faster then the next guy --also it feels like u are hook solid to the water.
    Osidebill was making the trim and steering extenders when guys were doing this on the GPRs. Maybe they are the same parts for the sho and we should shoot him a pm

  10. #10
    Happily Self-Employed WFO's Avatar
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    another plus with the 2" extension, you take a lot of stress off the crankshaft (and s/c clutch)

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