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  1. #1

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    Rotax Racing 2peice Drive Shaft - A Second Look

    This just seems to easy, and clean I just cant get it out of my head. So I purchased just the engine side of the RR drive shaft for around $200 to see what I can do with it. I have a few questions for rapidacceleration regarding how he set this up, and I would also like to hear others opinions on this.

    In the picture below, is the complete drive shaft kit, then the drive shaft installed in a boat. In this setup (as was intended for race use by Rotax) there is no support on the shaft, and that length is only 4-5" shorter than mine on the jet pump side of the coupler. If they have no balance problems in this setup, I just don't see why it wouldn't work for me. I did notice that this shaft uses a special coupler that eliminates the carbon ring. Which may be what makes this approach uneconomical. Maybe this adds the support that is needed to keep the shaft from wobbling. Or maybe it is a custom size, and thats why it replaces the carbon ring seal. I don't know, but I just discovered neither of my engines came with driveshaft/carbon ring seals, so I'll have to buy those anyway.

    On a side note, I'm really starting to get pissed about these "complete" engines I purchased that are missing a freaking laundry list of expensive small misc parts, and whenever I email the guy about it, he has the parts, and offers to sell them to me, after I already paid an extra $1000 on top of both engine prices to include "everything else" but thats a topic for another day...

    Rapidaccelleration: Was this the setup you used, the RR shaft? Or did you make your own coupler shaft?

    I may have leaped before I looked. I know nothing about the Drive shaft seals on Seadoo motors, nor this shaft. Does this shaft use the special seal as a support? Guess I'll figure all this out once it arrives.
    Last edited by boostaholic; 11-30-2007 at 12:43 PM.


  2. #2

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  3. #3
    Hydrotoys's Avatar
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    Anything can be made to work. Want me to move this over to the Seadoo performance section? That would be the correct place to get some feedback on this overpriced turd.

  4. #4

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    Want me to move this over to the Seadoo performance section? That would be the correct place to get some feedback on this overpriced turd.
    LOL!! haha Good call, please do.

  5. #5
    fabrication guru rapidacceleration's Avatar
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    well my stubb driveshafts where just like the rr unit..
    Sorry, i did dig up that box with 2 stubb shafts and a few PTO's but forgot to email you the pics...
    Ill try to get you the pics tonight. I just didn't have much luck with that setup. tried twice.. even tryed a solid coupler instead of the PTO's and it still vibrated at low RPM..... you may have better luck with yours...

  6. #6

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    Hmm, well the fact you tried it more than once, and never got it to work well isnt very promising. While I'm waiting on the useless RR POS then, I suppose I need to call Ted and see what he can fab up for me since I finally got an rxp driveshaft. Thanks for the input as always R-A, and please do send me those pics if u can.
    Last edited by boostaholic; 12-03-2007 at 10:43 AM.

  7. #7

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    Thoughts on the Design of the RR 2 piece Drive Shaft

    I know I just wont let this thing die, but it just seems a much cleaner and simpler solution to adapt the seadoo engine to the yamaha driveline. Maybe not, but I want to try anyway!


    I've been looking at this ALOT, and I think I've figured out why this one works without the vibration issues Dan had. Notice how the couplers are setup. (the $550 set of couplers I might add ) One of the couplers has moved the threads to the inner side of the coupler assembly. This would add 2 benefits. When assembled this gives you virtually shaft end to shaft end contact, without 2" of rubber in between to wobble around. And most importantly by supporting the rubber dampener around this inner shaft the rubber damper has much less side to side wiggle room since it is supported around the center shaft by the inverted coupler. From my research this shaft uses the standard carbon seal and all other bearings on the engine side, so there is no added support on the engine side. I believe the secret to why this setup works smoothly where a standard Yamaha coupler has vibrations is because of this special coupler design. This should effectively reduces the distance the couplers can "shear" by 1/2 being there is now 1/2 the amount of rubber to compress. The only other part of this is the pump side of the shaft, where they just secure the drive side coupler securely to the mid wall as the Yamaha already does. And add to this, how much more compact the drive line run is. All of these factors individually should help in reducing drive line vibration, together they allow this system to work well. As soon as I receive the RR engine side shaft and figure out what its threaded for, I'll have a coupler machined to be threaded into the inside of the coupler connection as the RR one is and share my results.

  8. #8

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    Well, I received the engine side of the RR 2 piece shaft today, and at first glance it didn't look any different from the splines on a OEM shaft. But when I test fit the shaft in the motor I noticed it seemed to seat more firmly, and had much less play. Which prompted me to look closer at it.
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  9. #9

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    And one more pic

    You'll notice the splines have been cut completely different from an OEM shaft. Most noticeably the ends of the splines are straight cut instead of being rounded off. This obviously fits the shaft straighter and with less play.
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    Last edited by boostaholic; 12-07-2007 at 08:32 AM.

  10. #10

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    There's a reason the shaft is rounded..... Vibration when the motor moves under load.

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