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  1. #1
    MPower's Avatar
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    What prop for these mods?

    Fellas,

    Next week I will be putting the following on a 2005 sportster:

    XS Intercooler
    4 inch Intake
    X Charger
    Rude RRFPR

    What prop will this setup require?


  2. #2

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    MPower- I responded to your PM, but might as well post it hear for prosperity and/or difference of opinion:

    You probably see in my sig that I have basically the same setup. I'm running a S.C. 15/20 (4-blade). It was perfect in the winter (in Florida, water temp 65F) at 8100rpms and 62mph. I started getting heat fade after about 20 minutes though, which was reducing RPMs by 150, and had to add the thermostat. That put me back perfect at 8100, but when the water started heating up, my RPMs went down. 78F water had me at 8000rpms, so I took 1 mm pitch out of the 15/20. I knew the water would only get warmer here, so I dumped the S3 SC and am going with a Rude.

    So the 15/20 was a challenge for me to turn with that setup, but given the X-charger is supposed to be a tad stronger than the S3 SC, and NC water is usually cooler than ours in Florida, I'd say an untouched 15/20 will be just right. May even have to add a bit of pitch in the winter. There's a 2mph difference on my boat between winter and summer.

    I'd say you could expect an average GPS run to be 62-63mph. If he finds himself over 8100rpms, he'll have to pitch the prop to see more speed. That's really the only prop solution right now. A 15/22 is supposed to be available this summer, but I'm thinking he'd need more than an x-charger for that.

  3. #3
    MPower's Avatar
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    If a 15/20 ended up being too much, which prop would be used? 14/19?

  4. #4

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    What I'd do if the 15/20 is too much (but like I said, it shouldn't be) is get the Rotax X-SC spacer and wheel, which starts approaching the power of a Rude, and then you will be able to turn it. If he had to drop down to using a 14/19, while the acceleration would be phenomenal, he would hardly ever be able to break past 60mph. The 14/19 would also have to be pitched up a good 3mm.

  5. #5
    MPower's Avatar
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    thanks scott 15/20R ordered

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