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  1. #1
    TheElite0ne's Avatar
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    Trying to Dial in prop pitch - Help

    Hey Guys,

    I have a Speedster 150 but the boat section doesn't get alot of traffic so I figured i'd have better luck posting here.

    I'll give you a break down of my progress.

    SPECS & Mods
    2007 Speedster 150 215hp
    4" Air intake
    X-Charger
    42lbs Injectors
    15/20r prop



    Speed with Mods - All speeds are GPS verified with the same GPS
    1. Stock Everything with only 4" Air Intake - [email protected]
    2. X-Charger, Injectors, Stock prop - [email protected] rev limiter(5/8 throttle) - water temp 72*
    3. X-Charger, Injectors, 15/20r prop - [email protected] water temp 72*
    4. X-Charger, Injectors, 15/20r prop repitched to 14/18 - [email protected] limiter (7/8 throttle). water temp 66*
    The 15/20r prop was to big for me so I had it repitched. Took 1* off the leading edge and 2* off the trailing edge. I guess this was too much cause i'm all over the limiter and have lost quite a bit of top end.

    The boat ran the best with the stock prop, even though I was all over the limiter.

    Any suggestions?

    Could someone educate me on prop pitch numbers? I don't really know what 15/20, 14/19, etc... actually mean. All I know is the bigger the number the more power I need to turn it.


  2. #2

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    You should probably start @15/22 you would like to be running below 8100

  3. #3
    TheElite0ne's Avatar
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    Quote Originally Posted by rxpstan View Post
    You should probably start @15/22 you would like to be running below 8100
    I could only turn a 15/20r to 7800rpm. Isn't a 15/22 bigger? wouldn't that lower my RPM even more?

  4. #4
    formerly Gold06RXP Turbo Nick's Avatar
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    Send it to Speedfreeks!!

  5. #5
    speedskixp's Avatar
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    Quote Originally Posted by rxpstan View Post
    You should probably start @15/22 you would like to be running below 8100
    Stan, he said that the 15/20 would only turn 7900rpms. I'm sure you missed that.
    I would pitch to 15/19 and see where that gets you. I have a feeling that you are fighting the climate. How much did the weather change from one test to the next. You are likely taking pitch out to get the 's up and at the same time the weather is getting cooler and the engine is making more power making it harder to get the pitch right. If thats the case you may be able to almost turn the 15/20 now.

  6. #6
    TheElite0ne's Avatar
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    Quote Originally Posted by speedskixp View Post
    Stan, he said that the 15/20 would only turn 7900rpms. I'm sure you missed that.
    I would pitch to 15/19 and see where that gets you. I have a feeling that you are fighting the climate. How much did the weather change from one test to the next. You are likely taking pitch out to get the 's up and at the same time the weather is getting cooler and the engine is making more power making it harder to get the pitch right. If thats the case you may be able to almost turn the 15/20 now.
    The water temp changed from 72* with the 15/20 to 66* with the 14/18. Its winter time in Florida so the water is only going to get warmer.


    What do these numbers mean?

  7. #7
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by TheElite0ne View Post
    The water temp changed from 72* with the 15/20 to 66* with the 14/18. Its winter time in Florida so the water is only going to get warmer.


    What do these numbers mean?
    NOt only water temp that needs to be factored. But also air temp, and bar. pressure.

    Your realitive air density (RAD) will change depending on air temp, bar. pressure, and dew point. This will chage RAD and will affect horsepower alot.

  8. #8
    TheElite0ne's Avatar
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    Quote Originally Posted by skoepp View Post
    NOt only water temp that needs to be factored. But also air temp, and bar. pressure.

    Your realitive air density (RAD) will change depending on air temp, bar. pressure, and dew point. This will chage RAD and will affect horsepower alot.
    I understand about the air density and how the weather effects horsepower.

    All I can say is that when I was stock I could go from winter to summer and my rpms would only change about 150rpm.

    I went from 7800 RPM full throttle to bouncing off the rev limiter 8160-8180 at 7/8 throttle. The water temp only dropped 6* and air temp maybe 10*. Tests were done less then 30days apart.

  9. #9
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by TheElite0ne View Post
    I understand about the air density and how the weather effects horsepower.

    All I can say is that when I was stock I could go from winter to summer and my rpms would only change about 150rpm.

    I went from 7800 RPM full throttle to bouncing off the rev limiter 8160-8180 at 7/8 throttle. The water temp only dropped 6* and air temp maybe 10*. Tests were done less then 30days apart.

    Ok, I would try to split the difference on your trailing edge of what it was out of box to where you have it bent to now.

  10. #10
    speedskixp's Avatar
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    Quote Originally Posted by TheElite0ne View Post
    I understand about the air density and how the weather effects horsepower.

    All I can say is that when I was stock I could go from winter to summer and my rpms would only change about 150rpm.

    I went from 7800 RPM full throttle to bouncing off the rev limiter 8160-8180 at 7/8 throttle. The water temp only dropped 6* and air temp maybe 10*. Tests were done less then 30days apart.
    The water temps are in the 50s now. I would prop to be close to the limiter in the winter and in the summer you should be around 8000 rpms. Your speed will come up when you can apply full throttle without being on the limiter. Your other option is to have 2 props for winter and summer so that you can keep the your r's in the optimal range.

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