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  1. #1

    Set-back impellers pictures and comments

    Wanted to improve my pump setup. After asking some questions, it appears that the Rotax 16 vein pump, which uses the stock drive shaft, is the best...it also is very expensive--around $2900. A Skat Trak magnum pump appears to be the second best setup, but will take some time to get tuned in perfectly...also costs less--around $1500. A third option, which I had not really heard much about, is a setback impeller. A setback impeller puts the trailing edge of the blades closer to the stator veins in the pump...1/8" closer or 3.175mm. Also sets the leading edges of the blades farther back...like a setback pump--although not nearly as much. In theory, the less distance there is from the back of the impeller blades to the veins, the less turbulence and the faster the water can get started traveling straight out the back of the pump. I was told to expect less cavitation out of the hole, improved acceleration and not much in the line of top speed increases.

    Ran the ski last weekend. Noticed less cavitation out of the hole...I still slip 4 times--instead of 7. Acceleration was better...ski pulled hard all the way up to max rpm. From 20 mph is was about 3 seconds and I was at 8550. No change in top speed. I sent my old prop in with my pump and had these new props pitched exactly the same as my old 3-blade. Top speed was the same at 8550 with the new setback as it was with my old prop. Water was flat with some boat wakes, so did not get a chance to check rough water hookup abilities. Also had the nose cone on my prop come loose and ski started vibrating badly, so had to quit for the day. Going to try one of Speedfreaks shorty nose cones and see how that works.

    Mark

    For those of you who had a double bearing mod done some time ago, Glen has better setup now and can modify the bearing and seal setup for you. The new bearings look huge and the seal is much improved.
    Attached Files Attached Files


  2. #2
    Moderator beerdart's Avatar
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    Great info as always..

  3. #3
    So, who's Glen? Whats the cost of these mods?

  4. #4
    suck my wake's Avatar
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    Quote Originally Posted by blkturbo! View Post
    So, who's Glen? Whats the cost of these mods?
    Glenn I believe is the owner of Skat-trak.

  5. #5
    Got out this weekend. Did get to ride through some chop this time out. The setback prop does increase hookup in the chop. I could feel the ski coming up through the chop and would be ready to feather the throttle when the ski came unhooked...but it did not come unhooked. I've had the ski for 6 years and know how much chop it can take before coming unhooked. There is no question it stays hooked up better with the setback prop. Thumbs up on the speedfreaks short nose cone also. Drive train is smooth as silk.

    Mark

  6. #6
    maestro's Avatar
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    Great info Mark. Thanks for sharing

  7. #7
    CHAD IBADTON's Avatar
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    +1 Speedfreaks

  8. #8
    maestro's Avatar
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    Quote Originally Posted by IBADTON View Post
    +1 Speedfreaks
    I sent him my prop. Cant wait to have it back...

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