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  1. #1
    Gus13letter's Avatar
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    Question RPM difference winter/summer??

    What differences in RPM have you seen from summer 80-90 degree air, 80 degree water to winter 60-70 degree air, 60 degree water?


  2. #2
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    Any updated GPS numbers today... it still shows 76.7

  3. #3
    Gus13letter's Avatar
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    Quote Originally Posted by bigdaddyRXP View Post
    Any updated GPS numbers today... it still shows 76.7
    Yup, here is my testing results, post 47. http://www.greenhulk.net/forums/show...617#post943617 Wasnt trying to hit top number, just testing rings vs rpm vs speed differences. 76.7 is my max speed so far.

  4. #4
    JFizzleJR's Avatar
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    I have seen on avg. a 300 RPM difference. I use a 15/20 and 81 mm in cold weather and a 15/20 -2mm and 83 mm in summer weather.

  5. #5
    Quote Originally Posted by Gus13letter View Post
    What differences in RPM have you seen from summer 80-90 degree air, 80 degree water to winter 60-70 degree air, 60 degree water?
    My spring riding with 60*F range air and 50*F range water to summer 80*F air with 70*F water I see a 200 RPM difference. Other factors come into play to, but generally speaking it's about 100 RPM per 10*F.

  6. #6
    Gus13letter's Avatar
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    Wow, pretty big differences. I was thinking maybe 100 rpm. Looks like I may have to have a winter and summer prop. Good thing I have a fairly new 13/19R sitting on the shelf for the summer that I can tweak. I was skeptical to have the one in the ski pitched any more because I wanted to see if I could make it work in the summer, but from the sound of it I may be too low on RPM in the summer. Here were my tests from today in a light chop water. As you can see I need to pitch the impeller for winter but if I do it will be way low for summer.

    80mm ring
    Holeshot rpm topped out at 8140rpm
    Max RPM 8180
    Top speed 76.5MPH

    81mm ring
    Holeshot rpm topped out at 8180rpm
    Max RPM 8200
    Top speed 76.3MPH

    82mm ring
    Holeshot rpm topped out at 8200rpm
    Max RPM 8220
    Top speed 75.8MPH

  7. #7
    Yep, the best my stage 2 setup ran was last spring, touched 76mph again and again. No way that's legit. Added GH box, RR wheel and spacer, ran 76mph all summer. WTF?! It's the conditions. I bet if I ran my current setup this spring I could touch 78mph if propped correctly, but like I said it wouldn't be legit.

  8. #8
    Gus13letter's Avatar
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    Quote Originally Posted by RXP-REX View Post
    Yep, the best my stage 2 setup ran was last spring, touched 76mph again and again. No way that's legit. Added GH box, RR wheel and spacer, ran 76mph all summer. WTF?! It's the conditions. I bet if I ran my current setup this spring I could touch 78mph if propped correctly, but like I said it wouldn't be legit.
    Well, I have made some changes since the summer so the setup now isnt what I had in there. That is why I asked about the RPM differences, so I know what to expect in the summer and if I should pitch this prop to be strictly a winter (what winter we get in FL anyways ) prop.

  9. #9
    SeaGoat's Avatar
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    Up here in North Carolina I was running 8040-60 in the summer heat. Went riding in december with air temps in the upper 50's and water around 51 and was hitting the rev limiter at 3/4 throttle. Temperature makes a huge difference.

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