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  1. #1
    somefun's Avatar
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    Speed vs. Rpm? Ipellers

    Guy's I have a Speedster S200 with custom 3" intakes and K&N filters , RR racing ECU, (2) External Intercoolers and filled ride plate holes. The boat stock was running 58.7 on a GPS. Now after all the mods it runs 66.8 was the best at 7800 RPMs. So I got some new impellers from Glen at Skat. I went from 4 blades prop that were 10/21's to three blades props that are 13/17's. I took it out today to test and the air temp was about 75 degrees and humid from the best run I had previously made at 65 temp no humidity. And the boat ran 67 MPH at 8250 to 8300. My question is I gained 400 to 500 RPMs and only gained .02 of a MPH. Does this seem right? I'm not sure what my next step should be. What do you think? Is that all she wrote? Is there no more left? I think the boat ran better with the 4 blade props. PLEASE HELP!

    RR 4501 ECU's
    3" Custom Intakes
    XS Intercoolers
    3 Blade Skat 13/17's
    SS Wear Rings


  2. #2
    Yuji's Avatar
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    Hmm...I would have thought you would have gained a little more on top end, how is the acceleration now? Is there any vibration from the three blades? Did these get rid of your holeshot cavitation? I'm also wondering if the Solas "R" 4 blades would be a better impeller for us. Keep us posted

  3. #3
    somefun's Avatar
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    Acceleration is good but I think the stock was better. Remember it was a 10/21 vs. 13/17 I think I may have the stock repitched to 10/19 and leave it at that. I think my cruise speed is slower now also. not sure on the hole shot because I picked up some junk in the jet after the top speed run and it would cavatate. I'm going to run it this week end and then call Glen and see what he thinks.

  4. #4
    Yuji's Avatar
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    Yeah..I wonder if you were to try re-pitching your stock ones and see what you get. I'm sure you've read the "how to re-pitch" sticky or send them to Glen and have him do it. Unfortunately you and I are the test monkeys for these things...but, when it's all said and done we should have some smokin' boats to show off

  5. #5

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    Switch your intakes to 4" and I bet you gain nouther 150-200 RPMS....

  6. #6
    somefun's Avatar
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    Do you think there is that much difference from 3" to 4"? Don't you have to neck it down at the supercharger anyway?
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  7. #7
    somefun's Avatar
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    Yuji did you get your back together yet? Any testing info?

  8. #8
    Yuji's Avatar
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    I haven't recieved anything yet...but I did tackle re-pitching 101. I posted on your other thread.

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