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  1. #1
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Impeller selection for the nasty 15f

    If anyone is staying up to date on my 15f project I took it to the water today and it ran about the same speed as my 12f (58 mph). It ran this speed at 5500 rpms and pig rich. The setup is as follows

    15f motor (warmed over)
    stx hull
    155mm Ultra 250 pump
    155mm Ultra 250 stock prop

    I am somewhere between 160 and 210 hp and can adjust my jet nozzle from 82-85 mm (today I was using an 84mm)

    I have my rev limiter set to pull timing at 8100 cut spark at 8200 and cut fuel at 8500 because I am using stock connecting rods.

    The stock ultra prop was only turning 5500 rpms I know that I have more power than a stock lx so I am not sure where to start Do I try and pull pitch off the 250x prop or do I pick up a lx prop and bend it up?

    What are the base pitches for the lx and 250?

    I know you can't compare a skat pump to a 250x stock but it looks like the endurance kit (cams and pistons) uses a 9/17 from riva.
    Thanks

    Sean
    Last edited by smokeysevin; 08-26-2012 at 06:31 PM. Reason: skat skat skat


  2. #2
    Moderator #985 lasportsmn's Avatar
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    I really think that one I have will be your ticket.

  3. #3
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    Impeller selection for the nasty 15f

    Something pitched between the 15f and LX would be a good starting point. It's hard to pitch a prop down. Good job on getting it out there and running.play with the pump rings to.

  4. #4
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    I hope I will be able to test the prop this weekend, I was checking the ski over a little while ago and I need to revise my exhaust because I nearly burned through the hose connecting the header to the tube.

    Sean

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    Moderator #985 lasportsmn's Avatar
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    WOO HOO
    I bet you were smiling the whole time.

  6. #6
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Re: Impeller selection for the nasty 15f

    The video doesn't do the ski justice of how loud it is. I may be crippled this weekend because the exhaust burned almost all the way through the connector.

    Sean

  7. #7
    Moderator #985 lasportsmn's Avatar
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    I had a problem with my LX burning the coupler and it was the rings on the connection from the manifold to the WB. Are you running a WB in the ski?

    Not sure of your setup but the parts I am talking about is #43058
    http://partsfinder.onlinemicrofiche....pe=13&A=30&B=7

    If they are not perfect they will burn the coupler instantly. When you install them wrap them in a single wrap of freezer take to hold them in place while you connect it to the WB. The heat will dry the tape up and it will just disappear.

  8. #8
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    Impeller selection for the nasty 15f

    Quote Originally Posted by smokeysevin View Post
    If anyone is staying up to date on my 15f project I took it to the water today and it ran about the same speed as my 12f (58 mph). It ran this speed at 5500 rpms and pig rich. The setup is as follows

    15f motor (warmed over)
    stx hull
    155mm Ultra 250 pump
    155mm Ultra 250 stock prop

    I am somewhere between 160 and 210 hp and can adjust my jet nozzle from 82-85 mm (today I was using an 84mm)

    I have my rev limiter set to pull timing at 8100 cut spark at 8200 and cut fuel at 8500 because I am using stock connecting rods.

    The stock ultra prop was only turning 5500 rpms I know that I have more power than a stock lx so I am not sure where to start Do I try and pull pitch off the 250x prop or do I pick up a lx prop and bend it up?

    What are the base pitches for the lx and 250?

    I know you can't compare a skat pump to a 250x stock but it looks like the endurance kit (cams and pistons) uses a 9/17 from riva.
    Thanks

    Sean
    58mph not to bad ether Sean pretty much same as stock 15f but a great start.

  9. #9
    Moderator #985 lasportsmn's Avatar
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    Did you open up more air flow to the ski? They starved for air before. Now it seems it would require more air than before. THis could have been a problem. Try it without the seat. It was sounding like it was bogging to me at the higher throttle positions. I may be completely off with this and my brain is preoccupied but that was a thought I had.

  10. #10
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Re: Impeller selection for the nasty 15f

    I was not running a water box bit I'll need to this weekend because I won't be able to the the new HTS couplers in time.

    Yes you are correct GL its bogging really bad I was maxing out my AFR gauge and for now the hull is running no additional air other than the seat bucket and seal removed and the hoses pulled. It does need more for sure but I couldn't go above half throttle without maxing the aft gauge, so 58 at half throttle ain't bad either. Its a tune problem at this point.

    I need to pull the spark plugs today and see if they are all getting the same color.

    Sean

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