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  1. #1
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    Back to back test on nozzle today

    FYI.
    I just did a back to back test today on two differnt nozzles. Now remember I am running the old 2002 pump, with concord impeller so this I know is useless to most of you guys. But mine in heavy chops, and a strong cross wind (I test on a smaller lake 3/4 mile across).

    2002 cone measures 86 mm should be a 87 right?
    2005 cone 85 right?

    85 cone 74.4 mph not as good of a hole shot (not even close)7250 rpms
    87 cone 74.3 mph great hole shot.7290-7300 rpms
    The newer cone changed some thing? ain' sure what but it started bucking at 74.1-4 mph. I'm not sure why but it started to almost feel like it was hopping.
    this is just and fyi. this was a true back to back test!

    The jetting did the trick also for the few that run a 1390 like mine( groupk with VF-3's, stuffers (yes the little white ones), and key way.

    I did a wide open plug check looked real good like # 19 on the chart
    I did one at little over 1/2 to 3/4 thottle and it looked like #18

    pilot is at 100, 1.5 needle, 131.3 main 95 gram spring.
    I am out 2 on the highs.
    out one on lows.

    This where I am at for those that asked.

    be cool


  2. #2
    Interesting, you want to get it jetted so that you're only 1 turn out on the highs, not 2. I would go to bigger jets.

  3. #3
    GPRPITMAN's Avatar
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    You need to put the 125's in if your out 2 turns. But before you do that you can put some kick in that prop lower your rpm's a tad and you will gain at least 1 mph Then when you kick your prop you will need to check your plugs again because as soon as you put more load on that motor it will also need more fuel

  4. #4
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    Quote Originally Posted by GPRPITMAN View Post
    You need to put the 125's in if your out 2 turns. But before you do that you can put some kick in that prop lower your rpm's a tad and you will gain at least 1 mph Then when you kick your prop you will need to check your plugs again because as soon as you put more load on that motor it will also need more fuel
    I will do.

    did i miss understand the carb manule? I thought out on highs was more fuel? I started at 2 out I had not fine tuned. because of the rpms.

    I have the super BN carb manule.

  5. #5
    Yes, out on highs is more fuel. If you already have a 131 high speed jet, why would he want to go to a 125??? You need a LARGER JET, which would be a 135. With the larger jet size, you should be able to get the screw closer to 1 turn out.

  6. #6
    GPRPITMAN's Avatar
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    Yep I screwed up on that, meant to say go up cause you were 2 turns out my bad sorry about that

  7. #7

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    Good job on the testing, sounds like you did a nice true back to back test.

    Your results are very similar to what I've found on my tripple even though they are way different ski's.

    Did both of the nozzles have the siphon tube still in them?

  8. #8
    Results were almost identical for me. Only .2 loss for me with the 87, and terrific difference in accelleration... 87 all the way for me..

  9. #9
    Chine Walker
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    I'm confused with the nozzles sizes. What size does the 2003 GPR come with?
    Do you need to change the impeller if the nozzle is changed?
    thanks,
    jp.

  10. #10

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    Quote Originally Posted by jpa1300 View Post
    I'm confused with the nozzles sizes. What size does the 2003 GPR come with?
    Do you need to change the impeller if the nozzle is changed?
    thanks,
    jp.

    I think all 1300's which would be 2003+ come with an 85 mm nozzle, all 1200's had the 87mm.
    The only reason to change impellers is if your rpms are not in the power band. Usually a nozzle change doesn't affect rpms enough to cause that problem.

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