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  1. #1
    www.ozpwc.com nello's Avatar
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    GTR215 Performance Help

    Previously had RXTX255 with only ECU reflash doing 72mph. Upgraded to newgen doo and chose GTR because riding RXTX260 felt too big and not a good replacement, and RXPX260 is the biz in looks but its a 2-seater which would limit recreational fun. Have found GTR hull is a perfect replacement for prior TX, alot more comfortable and alot more fun carving corners up. Very very happy with it. So now enhancing to make my own GTRX260.

    Mods Round 1:
    - Worx sponsons
    - X charger
    - ECU reflash to 8300 rpm

    Stock prop was cavitating badly in hole shot and hitting rev limiter constantly; so dealer suggest Solas 15/20 prop but didn't want to spend much more at the time, so we tried X prop. It improved hole shot (no cavitation) but dropped my revs right back to 8040-8080 and only 68mph. X prop then repitched 1mm and got 8140-8180 and 69mph. This was enough to pip stock RXTX260 and RXPX260.

    But I'm after 72mph, so dealer suggests 4" air intake ahead of new prop given X prop was doing better. Also I think the X prop may have been pitched back to original to accommodate 4" air intake (need to confirm).

    Mods Round 2:
    - Worx sponsons
    - X charger
    - ECU reflash to 8300 rpm
    - X prop
    - 4" air intake

    Out on flat salt water bay ride was doing 8240-8260 rpm and 68-69mph. Spoke with dealer, was surprised 4" didn't raise top speed and says will need to change prop recommends Solas 15/20.

    Racing friend was trying different props on his GTI (same hull) in fresh water arena so I went along and we tried a few changes, here are the results:

    X prop: 8140-8160 rpm, 69mph (why less rpm then in bay ... fresh v salt water?) Also noticed revs would drop back a bit rather than hold steady.
    4 blade Solas 15/20: 7660 rpm, 67mph
    3 blade, think 15/18-19: 8160-8180 rpm, 68mph (good hole shot, probably felt best of the 3 trials)

    Friend also had a Solas 15/22 but this dropped his revs back by 500rpm so we didn't bother trying it on mine, assumed same thing would happen.

    Had I put 15/20 in from dealer seems I would have been disappointed. So what do you guys think I need to do prop wise to get my revs up and 72mph?


  2. #2
    Banned User
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    Morning Nelson! Long time!


    Salt water is 'thicker' than fresh... Speed drop is normal
    Rev drop seems to be limiter?

    I'd:
    Reflash for 98 RON (Aussie) but to suit a prop that I'd be comfortable with...

    Strange to see so much drop going from X prop, that X prop must have had a fair bit of pitch increase?

    My results:
    15/20 solas on: 4inch intake, 8040-8060 rpm, 72.5 mph fresh, ~71 salt.
    1/4 full tank.
    S3 hull.


    I'd also look at doing a comp test (leak down would be best), plugs, checking wearing clearance/wear,checking under hull for damage when off trailer.

    Others may have something more profound to say.

  3. #3
    www.ozpwc.com nello's Avatar
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    Hi napper! Ski is brand new 22hr, definitely no problem with wear, clearances, hull etc. Just noticed another thread with TX260 who added 15/20 and dropped 500rpm too. This is intriguing given the recommendation to go to this prop untouched.

    The 15/20 on Simmo's ski is perfect ... but his engine doing 8860/75mph. The 15/22 dropped his to 8500/74mph and the 3-blade (think 15/18-19) rev too high. So whilst I get the need to re-pitch/tune, need to at least start with a base prop that's suitable.

  4. #4
    TDR's Avatar
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    Mabey the GTR cant turn such a big prop? With such little mods. But Riva's website clearly states to use a 15/20 with there stage 1 kit, which is what your ski is at the moment.

  5. #5
    1-877-JET-PROS BigBoost's Avatar
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    The gtr is not a s3 hull there is no step in it so no big gain without that step and it has a bigger pump tunnel than the s3 thats why you never see the gtr buck at high speeds like the s3 hulls do, the scoop grate is your problem your pulling gobs of water in and the rpms are being pulled down from this. you need to try going back to the old grate and start there.

  6. #6
    surferd15's Avatar
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    I got: 39 hours GTR, only mods, 4 inch kana, resonator removed, vtech 8400, hitting 69 mph at 8060. Stock everything else
    Glad to see another modding the GTR, Im adding x charger and have solas 15/20 to go in but seems that is not a good choice. Seems like this ski is hard to get past 70...

  7. #7
    Could that be because of the design of the hull and the amount of drag in the water? Seems odd that all those mods only yield a 2-3mph increase. If that's all that there is to be gained, I don't see the point in modding mine...

  8. #8
    surferd15's Avatar
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    Nello any updates?

  9. #9
    SLASHER's Avatar
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    I would of tried the ET 127 wheel , I run it on my RXT X and my RXP .... The little wheel is cheaper and a drop in and has more boost than the X wheel ...

    Iam also looking to buy the GTR for the same reasons ... This will be interesting ..

    Is the GTR Better in the chop than the RXT X 255 ???

  10. #10
    Moderator boataddict's Avatar
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    I remember someone building a GTI with big hp last year and it didn't go very fast. I am pretty sure this hull hits a top speed wall around 75.

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