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Thread: GK 1390 BB

  1. #1
    OCFZR's Avatar
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    GK 1390 BB

    I just took my GPR out this weekend with a newly installed GK 1390 91 octane kit. I'm wondering what peak speeds everyone is running with this kit and what additional mods will help this kit. I have to say that I am very impressed with the results so far - Everything that Harry promised!


  2. #2
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    I'm running a 1390 GK,,, I ran 71.3 mpr today,, real choppy water. 7300 rpms 14/20 concord, r&d plate. I had to remove shims today because of chops I have a top speed of 73.9 at 7340rpms, but water was much differnt. and had one washer under the front of my ride plate (0.125 washer) with skegs on the plate,
    BUT THE RXP was dead nuts on me. first out of the hole, was the first across the lake, both of us had problems holding water.

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    OCFZR's Avatar
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    What other mods do you have? Your RPM's seem a little high for this kit with the 14/20 Concord.

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    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    that;s what it is, I pm d you, just protec filters belows and stuffers. duel fuel feed. It just planes real good

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    ABBOTT's Avatar
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    there is probably 2 mph in "rpm reduction" still being left on the table. Try a 14/23 Concord.

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    OCFZR's Avatar
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    My RPM's are at 7200 cold and 7150 hot right now. I think this is the target rpm for my motor. What affect would the 14/23 have on the RPM's? Also, what would an 05 pump and dynafly do for me?

  7. #7

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    It bears noting that ring sealing contines to improve over the first 10 operating hours, and smooth water peak rpms will often contine to increase during that time as a result. You may wish to complete that first ten hours before evaluating peak target numbers.
    Respectfully, Harry Klemm


    Quote Originally Posted by Ocgpr
    My RPM's are at 7200 cold and 7150 hot right now. I think this is the target rpm for my motor. What affect would the 14/23 have on the RPM's? Also, what would an 05 pump and dynafly do for me?

  8. #8
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    Quote Originally Posted by Ocgpr
    My RPM's are at 7200 cold and 7150 hot right now. I think this is the target rpm for my motor. What affect would the 14/23 have on the RPM's? Also, what would an 05 pump and dynafly do for me?
    If you looked at my first post.. I was right on 7220 at 4 hours at short burst.

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