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  1. #1

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    What is stopping my GTR from revving past about 7750?

    I've got a 2014 GTR215 (bought January this year), its done 16 hours and is completely unmolested, still in as new condition and well looked after.

    I've noticed that it pegs out at a maximum speed of 100 to 101km/h (60mph) with revs stable at a needle width under 7,800 (I've not had the revs showing on the digital display, will do that next time I'm out - this is from the tacho). It just sits there and wont rev past this. This is on a glass like lake, 22c. I've not seen it go any faster than this since I've had it (bought it new).

    There's no misfiring, no funny noises or behaviour, and it revs up to where it sits like a rocket ship.

    Taking it to my local friendly dealer who are a bunch of great guys, they've never heard of anything like this on a GTR before - they're going to check out the throttle position sensor to see if its receiving 100%.

    The impeller looks perfect, no noticeable wear..

    Any ideas what this could be?

    I love this ski, and its summer here!


  2. #2
    imp0ster's Avatar
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    low SC slip. They've really never heard of a low RPM supercharged ski?? REALLY?

    When I bought a brand new X-SC years ago factory slip was 70inch/lbs

  3. #3
    dpracing's Avatar
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    I agree. Ck the slip..........

  4. #4
    Kiwi spanner handler
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    Hope you dont mind me posting,I reset the throttle body and checked everything over and test rode it this morning (Sunday) and consistently saw 7980-8060 rpm on the small jetski lake.I never test rode it before hand as just to busy this time of year but certainly cant fault how its running now.Will ring [email protected] Mike Phillips Seadoo

  5. +1 by:


  6. #5

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    OK, Jason (my local friendly SeaDoo tech guy) posted the results he got from my ski in a small lake at sea level in our city above. Interestingly I took the ski up to where I usually play, a smallish lake (3km long) up in the mountains. Running the GTR flat out it peaks at 7760-7780 RPM maximum, and won't run any harder than that.
    Looking back through various posts on this site, I discovered this interesting calculator that determines the effects of humidity, elevation etc on performance: http://wahiduddin.net/calc/calc_hp.htm

    Putting the details on my lake (it's at 830m elevation, the test lake Jason used is effectively at 0) I see I'm only getting 90.9% of relative horsepower at that altitude!!! That kinda explains the drop off in max RPM's, although I'd have thought a SC would have mitigated a lot of that... I'm off to test in a lake a little lower level (320m) which according to the calculator should give me close to 98% performance.
    VERY interesting..

  7. #6
    Jason waterworks?

    As if he can log the ski and post a xls log of it.
    Then we can see what boost / ign and so on you have.

  8. #7
    Welcome to high elevation riding.

  9. #8
    JT jpt7779's Avatar
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    Pittsburg, Texas Lake Bob Sandlin
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    Quote Originally Posted by Crysoganus View Post
    OK, Jason (my local friendly SeaDoo tech guy) posted the results he got from my ski in a small lake at sea level in our city above. Interestingly I took the ski up to where I usually play, a smallish lake (3km long) up in the mountains. Running the GTR flat out it peaks at 7760-7780 RPM maximum, and won't run any harder than that.
    Looking back through various posts on this site, I discovered this interesting calculator that determines the effects of humidity, elevation etc on performance: http://wahiduddin.net/calc/calc_hp.htm

    Putting the details on my lake (it's at 830m elevation, the test lake Jason used is effectively at 0) I see I'm only getting 90.9% of relative horsepower at that altitude!!! That kinda explains the drop off in max RPM's, although I'd have thought a SC would have mitigated a lot of that... I'm off to test in a lake a little lower level (320m) which according to the calculator should give me close to 98% performance.
    VERY interesting..
    That calculator is very accurate and useful, more people need to take these parameters into account. The (RAD) Relative Air Density in your high altitude riding is a huge factor to performance.

    If you are going to ride mostly at that altitude, consider de-pitching your impeller or getting a Solas 15/20 to get your rpms up closer to 8000.

    Re-check all of your hose clamps for tightness.

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  11. #9
    Butcherboy's Avatar
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    Smile

    Quote Originally Posted by Crysoganus View Post
    I've got a 2014 GTR215 (bought January this year), its done 16 hours and is completely unmolested, still in as new condition and well looked after.

    I've noticed that it pegs out at a maximum speed of 100 to 101km/h (60mph) with revs stable at a needle width under 7,800 (I've not had the revs showing on the digital display, will do that next time I'm out - this is from the tacho). It just sits there and wont rev past this. This is on a glass like lake, 22c. I've not seen it go any faster than this since I've had it (bought it new).

    There's no misfiring, no funny noises or behaviour, and it revs up to where it sits like a rocket ship.

    Taking it to my local friendly dealer who are a bunch of great guys, they've never heard of anything like this on a GTR before - they're going to check out the throttle position sensor to see if its receiving 100%.

    The impeller looks perfect, no noticeable wear..

    Any ideas what this could be?

    I love this ski, and its summer here!



    hey mate,
    that does sound weird I have a 2013 GTR and running in perfect conditions I get it up to 106km.
    Looks like the limiter kicks in then for me. Didn't really check the revs but will next time. Where abouts I. Nz are you running it?

  12. #10
    Q in Arizona's Avatar
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    My max GTR RPM's where at 8040.

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