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  1. #1

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    8200+ rpms and impellar

    I am turning 8250rpm most of the time and sometimes 8300, with a slight turn I have seen 8400+. I have the stock repitched impellar from Impros.

    Now that I have the pulley I have cavitation on takeoff and this is the only place I get it. I did not have it before the pulley upgrade.

    Is there a known impelllar that will work? Should I get this one repitched?

    I really do not want to spend any more money on the ski right now on uncertanties. Somebody has to know the answer or can at least tell me is there a better impellar out there.

    Jason


  2. #2
    JET250's Avatar
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    I'm running the solas and since breaking 8000 rpm I get the same problem but I thinks it a combo of slight cavitation and rev limiter, my friends rxp which has a stock prop but cracks more rpm then me has the same issue, we think its just the weight of the craft getting out of the water. I'm a lil suspect on the wedge, I'm going to replace the pump seal ring and remove the wedge and see what happens.

  3. #3
    ou812's Avatar
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    I don't know much on the 250 pump platform but you might want the leading edge of the prop tweaked out more (opened up) to process more water & that should kill most of the cavitation out of the hole while bringing down 80 - 100 rpm or so on top & with the strong possibility of more MPH too.. Call dave @ impros & ask him what he thinks.

    Thats what I had to do on my RXP & i'm assuming props work the same on all skis as far as processing water.

  4. #4

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    I have an email in to Impros and I am hoping Dave knows exactly what to do. Other than take off the impellar is flawless. I would like to get the rpms down around 8000 and get rid of the cavitation + add some speed on top if possible.

  5. #5
    ou812's Avatar
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    Yup, you need more pitch!

  6. #6
    TEEBEE's Avatar
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    I got my pump and impeller back from impros on friday. Put everything back together and took it to the river to test and see if my cavitation problem on takeoff was fixed and walla, no more cavitation Woo Hoo I was sooooooo happy. It bugged the crap out of me when it was cavitateing. I tried replaceing the rubber pump seal where the pump fits up to the ski and re siliconeing the rid plate and pump shoeand no luck. One thing that i noticed before I sent my pump and impeller out and when I got it back was the gap between the impeller and the pump. There was a noticeable gap before and now the gap is so tight that the impeller looks like its going scrape the pump wall but it doesnt do to rewelding the impeller and free flowing the pump. If your haveing problems call Dave at Impros. It was the best thing I did for my ultra.

  7. #7
    TEEBEE's Avatar
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    Thumbs up

    Quote Originally Posted by JWilson View Post
    I am turning 8250rpm most of the time and sometimes 8300, with a slight turn I have seen 8400+. I have the stock repitched impellar from Impros.

    Now that I have the pulley I have cavitation on takeoff and this is the only place I get it. I did not have it before the pulley upgrade.

    Is there a known impelllar that will work? Should I get this one repitched?

    I really do not want to spend any more money on the ski right now on uncertanties. Somebody has to know the answer or can at least tell me is there a better impellar out there.

    Jason

    You need to send your pump with your impeller together to Impros so they can do the best job and make one part work with the other.

  8. #8

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    Quote Originally Posted by TEEBEE View Post
    You need to send your pump with your impeller together to Impros so they can do the best job and make one part work with the other.

    My pump and impellar just came back from Impros. I have less than 5 hours on the entire returned assembly. I did not have this problem until I added the 1 to 1 pulley. I hope I do not have to send the entire assembly back again. I really want to just ride for a while.

  9. #9

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    Quote Originally Posted by TEEBEE View Post
    You need to send your pump with your impeller together to Impros so they can do the best job and make one part work with the other.
    Thanks I do appreciate the suggestion.

  10. #10
    Vern's Avatar
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    JW, it sounds to me like you have covered all the basics on cavitation already, and your pump, wear ring clearance, and impeller are likely not the issue. We have the same problems with our RXPs quite often; go Stage 3 and most of us have cavitation issues that we never did before. With the increase in horsepower, it is very hard to tune out all the cavitation ... sometimes it is one of the tradeoffs to having a very fast ski. Sometimes putting a little more pitch in the leading edge will do it though as OU mentioned; go slowly tho, too much and you will kill the speed.

    Hey, your fuel tuning project thread was great also, congrats on that, and great write-up.

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