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  1. #1

    new member, gp1300 opinions, quesitions

    Hey everyone, new member here first post. So got a really good deal on a local 03 gp 1300 with some mods and only 70 hrs.
    Current mods
    top loader grate
    Cat delete and d plate
    Sola's 13/19 impeller
    87mm pump housing
    I adj. my sponsons to the bottom middle top from front to back and it handles way better.
    And after all this 68 on GPS and TONS of cavi. in hole shot and hard cornering and with 2 people forget lol.

    I plan on adding a ride plate a must obviously for a couple mph. That is what I'm gonna do first so I'd really like to know about that. Over the winter I'm really gonna get into it, installing the intake and freeflow exhaust. While I'm in there I'm gonna put an 06 header on it, an efi controller. a 14/21sb impeller with anti cavi. cone and an aluminium longer jet nozzle
    My questions are
    Will the 14/21sb impeller with the anti cavi cone basically eliminate my cavi issue?
    Is the 06 header worth it with all the other mods?
    Does the 13/19 impeller suck?
    Which is the better ride plate? Riva, r&d (pro tech)? Understanding that all plates have to be tuned.
    Is the jetworks mod “all that"?
    Does the ski OEM have 2 cooling exits, 1 on each side?
    Any other input or ideas would be greatly appreciated. Gotta beat my buddies rxp next season.
    Also are trim tabs really worth it? I read you can shim your stockers and get the same results.

  2. #2
    007GPR08's Avatar
    Join Date
    Apr 2009
    68mph is good for what you've listed.
    13/19 is for low & midrange acceleration. 14/21 wil be too much for stock power. You'll need to have your head milled to raise compression for more hp, and even then 14/20 is probably as much as you'll want to go. Also want to add an efi controler for more fuel & add oil to the tank or go premix 40:1.
    Forget about the FF exhaust, it will hurt your top end.
    To solve/help your low end acceleration/cavitation change to an '05 pump.
    Personal preference is R&D ride plate, and get Jims mod for more top end.
    Also, '03 has the weakest hull in the pump tunnel area so upgrade it first.

    Read through the stickies for guidance.

  3. #3
    OK would a 13/20 make a difference? I know the 05 pump is bigger, so switching that with the corresponding impeller size will help? The shaft too? Is that all that would need to be changed? I'll have to look into the tunnel reinforcements. As for the rideplate. I'm looking for the best of all worlds. Stability, handling, and lo mid top speed. I mostly ride well trafficked lakes and rivers. So I don't just want top speed and be porposing the rest of the time.

  4. #4
    OzarkYamMonster's Avatar
    Join Date
    Oct 2012
    Lake Of The Ozarks
    Hello waveflyer90, good choice on ski ... they can be beast. Only takes $$ & time LOL
    Most of what you already have is a great start.... yes get an R & D ride plate. You can make some grinds on it to get the angle that will serve your needs. There are several good threads on here that explain this procedure in great detail. Yes, to get more speed & rpm's you will need to mill your heads. I sent mine to Jim @ Jim's performance the total cost was only $ 100. and yes that included the shipping back to me .... a quick turn around less than a week. I now have 150 psi on all three cyls. I have the Jetworks mod, It does help with the hole shot but ... still need more. These GP1300R are know pigs out of the hole when up against most fast skis. Ask me how I know LOL Where do you live ? maybe a forum member who has Yamaha GP is near you.

  5. #5
    I live in the Chicago land west burbs. I mostly ride on the IL river where there are quite a few 40' boats kicking up a wake. I sometimes hit up the local fox river and other times I'll get up to a few lakes in WI.
    $100 is actually really good for the heads. But my plan is to not tear down the motor (yet) lol. The ride plate is my next mod, hopefully this season. Then the rest will be a winter project. Maybe I'll hold off on the impeller till I get the heads done then. Bit why does riva sell it with the 14/21 on the stage 2

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