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  1. #1

    04 RXP in 3m jetboat-blade selection - help please

    hi all

    i have an 04 rxp engine/jet unit in a 3mm jetboat hull.

    i have some cavitating issues from a standing start that i would like to reduce through blade change.

    as a boat is different from a ski both aerodynamically and weight distribution, the usual rules wont apply,the unit is running the standard rxp blade.

    would an rxp 255 blade increase or decrease hook up?

  2. #2
    lextoy's Avatar
    Join Date
    Jan 2007
    Brigantine, NJ
    what is a 3mm hull ?? do you mean 3 meter ??
    can you post a pic of setup.
    your cavitation is probably not due to impeller, but due to air leaking into the pump tunnel somewhere in front of the impeller.
    we need pics of pump tunnel, intake grate, thru hull fitting for the shaft, and general hull pictures,
    and tell us more about when it cavitates, at initial throttle up? a 3 blade prop gives better hook up at expense of speed.
    however i dont think impeller is the problem here.

  3. #3
    yes,sorry 3m hull,haha.
    i thought it might be air leaking through the carbon seal initially but there is alot of tension on it when i try pull it back,doesnt leak water there unless i apply pressure to it when on the trailer.
    the grill is a 6 bar grill (typical jet boat style grill) i took the grill off and tested without grill and made very little difference to the caviataion so i sort of ruled out lack of water flow.
    the intake is a custom alloy intake.
    i havent got any photos of the seal and intake but will take some and put it up. the boat is just in the shop getting a sand trap fitted.

    Click image for larger version. 

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  4. #4
    lextoy's Avatar
    Join Date
    Jan 2007
    Brigantine, NJ
    how is the wear ring? new? is it the correct size for the impeller ? they make 155 and 159 mm rings for the 155 and 159 mm impellers.
    there should be almost no gap btw impeller and wear ring, like a single piece of paper should almost not slide thru.
    what about venturi reduction nozzle and steering nozzle ?? all stock from sea doo?
    pump tunnel proper diameter ? aka at least as large as it would be on a sea doo?
    i am also thinking that hull looks pretty flat bottomed, does it air out the tunnel when the bow rises, or just generally , does tunnel get aired out very easily?
    i would look into adding some sort of aggressive scoop grate, and not to be funny but what about sponsons. last thing you want is trying to turn and the rear slides out and instant 180 spin.
    this is not a stock setup at all so some creative solutions may be necessary.
    i still doubt impeller will make much difference.
    pics of hull, intake area would be interesting, any deadrise at all on the v bottom, or basically just flat?

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