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  1. #1

    Join Date
    Sep 2017

    Driveshaft setup for Seadoo pump in Jet Boat

    Hi all,

    Thought I would come to the seadoo mods experts with this question.

    Im fitting a RXP pump to a jet boat using an automotive engine (Suzuki M16A - Turbo). Currently working out the driveline setup.
    Ill need to have something machined in order to couple the driveshaft to the engine, and was wanting a bit of advice.

    Thinking of either making a threaded adaptor and fitting a 4-tec PTO output sleeve to it, greasing it up and housing in some kind of rubber boot.

    Another option that I thought might work a little better is to have the engine side of a driveshaft threaded to accept a rubber coupler such as yamaha or kawasaki style then fitting this to the engine flex plate. The concern I have is will a rubber coupler keep the shaft concentric enough to stop vibration? Im planning on using the standard seadoo carbon ring and bellow setup and would fit the coupler inboard of this.

    Any pointers? Thanks very much in advance.

    Incase anyone is interested in the project I have a forum on NZjetboat web board.

    Kind Regards,

  2. #2
    I have used the Kawasaki type couplers however in high horsepower setups they tend to tighten and split from threaded area outward if Loctite ever fails and driveshaft tightens, also most of those use a center bearing/seal with rubber mounting making for a stabilized floating driveshaft. Not sure how well the Kawasaki couplers would fair with seadoo typedriveshaft seal setup. . I'm thinking the Heavy duty driveshaft that seadoo uses on supercharged skis is pretty heavy and I would go with seadoo splined coupler on rear of engine or tranny. JMHO>

  3. #3

    Join Date
    Nov 2015
    Auckland, New Zealand
    Might be worth a chat with these guys

  4. #4

    Join Date
    Sep 2017
    Thanks for the reply Guys,

    Think ill go down the seadoo spline path. Have ordered a 4-tec output sleeve and planning on having an adaptor machined that I can thread that onto and fitting a CV boot or something similar over and greasing the spline.

    I had seen the Seadoo 951 PTO spline adaptor and this looked almost exactly what I need but im told it won't fit the 4-tec driveshaft spline. Shame!

    Thanks again, MikeC

  5. #5
    swlamarshrunner's Avatar
    Join Date
    Dec 2014
    Lake Charles, Louisiana
    An adaptor that would look something like this? This is seadoo spark splines with yamaha threads on the other end

    25371379_10155985778813256_1119343441_o by Ricky Hinch, on Flickr

  6. #6

    Join Date
    Sep 2017
    Adaptor would look much like the seadoo 951 PTO but as I believe the spline on this guy is only 17mm not the 22mm output of the 4-tec I would need to make my own from a 4-tec output sleeve

  7. #7
    wkuadam07's Avatar
    Join Date
    Feb 2013
    Bowling Green, KY
    If you don't align the pump shoe to the through hull and the engine to the pump correctly with the seadoo alignment tools you are asking for a sinking...
    The carbon seal is the bunion on the side of Seadoos foot when things aren't aligned properly... Do yourself a favor and build a bearing carrier type seal like yami or kawi and use the lovejoy shaft coupling like them as well. Much easier to align, much easier to work on later. This way when you go to pull the engine you don't have to pull the pump and do an alignment, you align the lovejoy with feeler gauges and an indicator.

    Look at the rated RPMs and torques on these...
    300hp @ 8000 RPMs is only about 8in/lbs by the way... Those parts are known industrial commodities... not things welded up with guesswork. They are remarkably cheap too...

    OR this looks like it would be a promising start as well...
    but it's mighty $$$ pricey. It already has splined pcs and a bearing carrier all made up for you. They even have through hull seal carriers available.

    Just my thoughts...

  8. #8

    Join Date
    Sep 2017
    I have been looking at using a rubber donut from an automotive prop shaft like this one. They have a centre pin that goes into a bearing aligning the shaft with the engine side but allowing miss-alignment and a bit of torsional dampening

    Issue with this setup is making a drivehsaft side hub that will attach to the driveshaft and be removable to allow a through hull bearing to slide over the motor side of the driveshaft due to the impeller side being quite large.

    I would really like to find a working example and just copy that.

    Cheers, MikeC

  9. #9
    Mike c did you ever make one of the coupler setups for the Seadoo 4 tec that you were talking about?

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