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  1. #1

    Question from an RXP guy to a GPR guy!

    My buddy has an 06 GPR1300 and was wondering what it would take to run a consistent 75-76mph. We were out on the water this weekend and i ran into a couple older guys on 03 GPR1300's and well. I ran em and i beat the one guy who was a bit heavier and the skinnier guy got me in the end he gps'd at 75 that day and me on my RXP i can usually pull of a 73.7 and a 75 on a cold day but yesturday was 100 degrees. I also had a full tank of gas and he had 1/4 tank. So weight clearly was and issue and i probably weigh about 30lbs more than him. They tryed telling me and my buddy who has a the 06GPR that they were stock , acting like little kids hiding a secret when really i didnt care i was just trying to help my friend out and they wouldnt even tell him . So my buddy wanted me to ask you guys what it would take to get to a consistent 75-77mph. Thanks guys


  2. #2
    Happily Self-Employed WFO's Avatar
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    First you know its hot... speeds will vary and be much lower in 100 degree heat than in 75 degree weather (like 2+ mph slower).

    Porting would help to insure you can run 75-76+ in most any weather or most any conditions (except for big chop), but its more than most want to get into ($$$) for a rec. ridden ski. Also some boats are faster than others, so results will be up or down a mile or so because of inconsistencies in hulls, shoe height, etc. Fuel level plays a role in top speeds as well (like 1.5-2.0 mph slower full tank vs 2 bars fuel).

    On an 06 to try to run 75mph consistently you will at a minimum need reeds, timing advance keyway, higher compression, air filter, air mods, EFI controller, D-plate, DynaFly prop (not right outta the box), angled rideplate, and 800 intake grate. That's for mid to top end with flat water. And that's just the parts. You still have to tune them to the boat.

    If you are going to try to muscle them from the holeshot to 75 it gets harder. You will also need to seal the pump, jetworks mod, run a 1200 grate, and someone to setup the entire boat correctly.

    Bigger pistons and porting would easily do the job. Other tuners may have other comments, but that's how I personally would approach your goal with out going too deep into the motor.

    Also remember that when you add speed, you add maintanence... and a tunnel reinforcement is a must do.

  3. #3

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    + VF3 reeds ????

  4. #4
    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by kevski View Post
    + VF3 reeds ????
    Absolutely

    (or IIs if you prefer )

  5. #5
    KamikazeGPR's Avatar
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    I was hoping someone would ask this question as im stuck on the fence here as what to proceed with.

    I have a stock motor 06. Out of the crate it gps'd at 65.9-66.3 best. With the addition of jim's package spec plate(not new FF plate),ppk and 1200 grate. It gps'd at 69.7-70.2 best. This was in january up north,air temp 65 degrees,water temp 50 maybe.

    OK, here we are in july. 90's temps and humid.same setup with the addition of cutting out the plastic under the fairings.im just cracking 69 with the 1200 grate, and just over 70 with the 800.Which is fine for a stock motor.Im down about 1mph with the temp changes,its expected.Almost forgot,im using R&D full lenth sanded tabs(not helping top speed,but i like the ride in chop)

    Im considering installing the next set of parts i currently have(VF3's,milled stock head,efi,R&D race filter(still debating on keeping stock gutted airbox)14/20 out of box dynafly(I'd have carl work it over b4 i put it in)

    Yesterday i deceided to put the pet2100 on and see what my rpm's are.7300-7320 in 92 degrees and 50% humidity. Is that what other people are seeing out of thier 05 and higher stock 1300's? I know the reeds will give me another 100 rpm or so and theres a few other tricks to squeeze out 30 here and there.(my rpm readings were on a 3 hour heat soaked motor)Still running cat-con,will change it out when i do the reeds.

    How high should your rpm's be on a stock motor to accept prop changes.I guess what im asking is: How many rpm's would i lose to just put a trued 14/20 dynafly on my ski as it sits now stock.

    Next question: how many rpm's do i need to move up to a 14/22 dynafly assuming i have all the other forementioned parts on. Im just trying to figure out where i have to be so i dont have to keep sending props off to be re-pitched.

    My goal is 75-77mph and totally bolt on.I put alot of hours on(83 on the 06 in a year)I have a 4 year extended warranty, so it has to be reversible in a few hours work(no big bore,porting, ect.) My dealer is cool,but yamaha isnt that dumb when it comes to repair.

  6. #6
    All hail the Chief! fullboogie's Avatar
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    To add to what Rich (WFO) said, you can't throw parts at a ski and expect it to perform. There's lots of tweaking you have to do to various parts to make it all work. In other words, you should really be "into" skis if you're going to attempt a 75 mph ski.

  7. #7
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by fullboogie View Post
    To add to what Rich (WFO) said, you can't throw parts at a ski and expect it to perform. There's lots of tweaking you have to do to various parts to make it all work. In other words, you should really be "into" skis if you're going to attempt a 75 mph ski.
    EXACTLY!!!!!! And you cant get pissed when it wont run as fast as someone elses ski. I am there and doing that right now.

  8. #8
    Happily Self-Employed WFO's Avatar
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    From what I have seen on most of the non-PVs... stock prop, air mods and 1200 grate (and D-plate) turn 7300-7350. The Dynafly will drop you to 6950-7000. Maybe a tad higher or lower.

    With your next level of mods, the 14/22 should be about right. Also consider everybody pitches props a little different, so Carl's 14/23 may be closer to a Fercho 14/22.

    JMO

  9. #9
    KamikazeGPR's Avatar
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    Thanks for the reply.Its nice to know im in the right stock rpm ballpark.

    With the next level of mods and all the rpm tricks.what is the target rpm range with a trued 14/20----14/22....im sure you're way up above 14/22 on your skis.

  10. #10
    All hail the Chief! fullboogie's Avatar
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    Listen to Rich - he's one of the most knowledgeable people out there in the GPR world. He won't steer your wrong.

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