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  1. #1

    Impros 13/21 Repitched - STX-15F

    From my searches, this impeller is little discussed, but seems like an interest setup. It starts as a 13/19 casting and is tweaked up to a 13/21. From what I've heard it offers better hook up and some more on top as well. I would love to hear some feedback if anyone is running it on their STX15f and any comparison to the more common 14/21 that is recommended by Solas and included in Riva's RPM Kit.

    Thanks!


  2. #2
    RLACEMAN's Avatar
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    I have tried the following Solas impellers, 14/21, 14/20, 13/19 & 13/20. 13/19 has the best hole shot, 13/20 great hole shot, but with a slight cavitation & has best top end speed, 14/20 has the same top end speed but the hole shot suffered, the 14/21 was the worse of the bunch, it had weakest hole shot & top speed was slightly less than the 13/19, it lowered the rpms down too much starting to get out of the peak power band. So I am using the 13/20. I would like to also try a Skat-Trak 13/19R, I haven't read of anyone on this site who has tried one. All of these impellers I had done by Impros except the 13/19, they start with a 14/21 & 'tweak' it down. Also I am at 875ft above sea level when testing, one time I was in Florida with the ski & at sea level I could have used one more degree higher pitch as the rpms were about 150-200 higher, at that time I was using the 13/19.
    Last edited by RLACEMAN; 06-06-2015 at 12:49 PM.

  3. #3
    Thanks RLACEMAN - this is really useful feedback.

    Just some context. I am about 155lbs with gear and soaking wet. The lake I ride is about 600ft above sea level. Sounds like the 13/20 is probably the best setup.

    I wonder if the newer 15F's have any more power than the earlier version that used the dual water box setup?

    Also did you notice any drop or increase in fuel economy with the impeller change? Any difference in the characteristic of the craft while cruising?

  4. #4
    RLACEMAN's Avatar
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    All the mods I have done are listed in my signature, my ski is a 2006, & I am about 230 with all my gear. I did notice a slight increase in fuel economy going from the 13/19 to the 13/20, the only difference in cruising is a slight drop in rpm at all speeds, this is where the extra fuel economy comes from. I think the newer skis with the single waterbox do run a bit stronger, many people are saying they are getting about 62mph with no mods, the older ones were about 1 to 1 1/2 mph less, the newer ones also use a different ECU which may have a better calibration for power/economy.

  5. #5
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    I am going to be testing back to back a few props in the next week on a stock 15f, I will be able to give you some more feedback. One of the props I am really excited to try is a stxr 12-25 dynafly with a bigger nozzle.

    Sean

  6. #6
    Sean,

    How did your testing go? How did the dynafly and nozzle combination work out?

  7. #7
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    I have been waiting on a set of piston rings to come in so I have not gotten to test anything yet. I will update when I get the motor freshened up and on the water.

    Sean

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