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  1. #11
    robk's Avatar
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    I sent my prop to impros (scat 13/23) running 7900rpm. I told them I wanted better holeshot and 300-400 more rpm's on the top end. Its coming back as a 14/19. Will install tomarrow and run Sat.


  2. #12
    Moderator RX951's Avatar
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    Quote Originally Posted by 2fast4u View Post
    I have preached about getting the correct rpm's and prop pitches on your target rpm's. Now for my second sermon. When you are trying to get your rpm's correct you need to know just what prop pitch you actualy have. I have seen almost every brand and type of prop made and none of them are what the Mfg. said they were supose to be. The only way to know what you are dealing with is to put the prop in a pitch gauge and read all three blades both on the trailing and leading edges. There are a lot of good guys out there re pitching props. The tru prop pitch is the only way to start and go from there to get the end results you want. I see on the forum guy #1 has the same mods as guy #2 and has a ??/?? pitch prop and guy #2 try this same ??/?? prop and can't turn the rpm's guy #1 can. Well guess what even though both props have the same pitch numbers on them they are totaly different pitches. To make things worse some guys who re pitch props don't go up on the blade when re ptching as far others do and this also changes rpm's some too. So what is a guy to do? Try to get as close a pitch prop as you can to start with and try to get it repitched even one to three times till you get it correct for your rpm's, if you miss your target rpm's more than 450 rpm's or more you have got the wrong prop for your ski to start repitching on. Another problem for you guys to face is if you add more mods to your ski latter this prop prop is wrong also and usualy will require a different prop again. I just want to let you guys know why we see so many prop questions. Lets pray that everyone get the correct prop the first time! Amen, Tommy Jordan
    Quote Originally Posted by JIM'S PERFORMANCE View Post
    Your not kidding Tommy i hardly ever see the impeller being what the mfg. says it is.
    yup. I've seen three impellers brand new out of the box all identical pitches all read different. Also, depending on who it pitching them, that can be a factor as well too. And to add, everyones setup is different.

  3. #13

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    bump this back up to the top for the new guys

  4. #14
    Are the impeller manufacturers at least consistent in their incorrect pitches? I don't really care if the 13/18 impeller I have is actually a 13/20 as long as when I order a 13/19 it is actually a 13/21.....

  5. #15
    lets race.... mikeFZR's Avatar
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    In my experience the trailing edge for skat is one degree less than what they advertise. IMO any prop will require some tweaking.

  6. #16

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    Quote Originally Posted by allstar71 View Post
    Are the impeller manufacturers at least consistent in their incorrect pitches? I don't really care if the 13/18 impeller I have is actually a 13/20 as long as when I order a 13/19 it is actually a 13/21.....
    The quality of scat or solas impeller out of the box are extreamly bad at best. I have seen all three of the blades different from each other not to mention they don't even matched there advertised pitch at all. Dave at Impros ( www.impros.com) seems to be the most conscent on his pitches. I think he takes the time to correct these poor quality props befor he ships one out new even if it is a box stock prop ( not a race preped prop) you are buying from him. Tommy Jordan

  7. #17

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    bump back up for the new guys

  8. #18
    mikevv's Avatar
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    Quote Originally Posted by 2fast4u View Post
    I have preached about getting the correct rpm's and prop pitches on your target rpm's. Now for my second sermon. When you are trying to get your rpm's correct you need to know just what prop pitch you actualy have. I have seen almost every brand and type of prop made and none of them are what the Mfg. said they were supose to be. The only way to know what you are dealing with is to put the prop in a pitch gauge and read all three blades both on the trailing and leading edges. There are a lot of good guys out there re pitching props. The tru prop pitch is the only way to start and go from there to get the end results you want. I see on the forum guy #1 has the same mods as guy #2 and has a ??/?? pitch prop and guy #2 try this same ??/?? prop and can't turn the rpm's guy #1 can. Well guess what even though both props have the same pitch numbers on them they are totaly different pitches. To make things worse some guys who re pitch props don't go up on the blade when re ptching as far others do and this also changes rpm's some too. So what is a guy to do? Try to get as close a pitch prop as you can to start with and try to get it repitched even one to three times till you get it correct for your rpm's, if you miss your target rpm's more than 450 rpm's or more you have got the wrong prop for your ski to start repitching on. Another problem for you guys to face is if you add more mods to your ski latter this prop prop is wrong also and usualy will require a different prop again. I just want to let you guys know why we see so many prop questions. Lets pray that everyone get the correct prop the first time! Amen, Tommy Jordan
    Tommy
    I completely agree with your point that you need to know what you have. If you look at the speeds and mods database on this site you can get pretty confused.
    I have a related question that tries to take the prop angle out of the equation. If you look at the speeds and mods database you see very similar mods at a given speed but at very different RPMs. For example, if you pick 80 MPH as a reference and look at the RPMs people are posting to get those speeds it varies over 700 RPMs. I know there are a lot of variables that come into play but I thought the RPM to MPH relationship would be more linear.

    1) The RPMs are not accurate? (See Motec/C5 at 8850 RPMs and 80.1 MPH or R2/B1 at 8180 RPMs and 82.4 MPH)
    2) The speed was not done with a GPS?
    3) Some other mod produced enough power (or less weight and reduced drag) that the setup allowed a higher speed with less RPMs?
    4) There are just too many variables?

    Your thoughts?


    Mikevv
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  9. #19
    Yellow93's Avatar
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    One way to answer that is this: Some people are trying to run 80 with a stock or C1 supercharger wheel, to do this they have to turn a higher rpm to in turn get more boost out of these lower psi wheels, and they do this by pitching the prop to get the rpm they need to run the number. On the other hand someone that is running an E1 or 15.5 ET wheel wouldn't need to spin the motor as high to get the same mph because their wheel is making boost a lower rpm.

  10. #20
    YAMAHA POWAAAA !!!!! 1_Fast_SHO's Avatar
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    Quote Originally Posted by Yellow93 View Post
    One way to answer that is this: Some people are trying to run 80 with a stock or C1 supercharger wheel, to do this they have to turn a higher rpm to in turn get more boost out of these lower psi wheels, and they do this by pitching the prop to get the rpm they need to run the number. On the other hand someone that is running an E1 or 15.5 ET wheel wouldn't need to spin the motor as high to get the same mph because their wheel is making boost a lower rpm.
    Agree, always believe in high boost with low RPMS, scare to spin the motor so HIGH

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