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  1. #1
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    Testing the Allison Grand Sport with a Mercury 150 four stroke

    Preliminary testing and where this project is going. Better results than I thought out of the box. Got some work to do to get it where we want it, but promising.

    https://www.wavetowave.com/home/2018...-a-mercury-150



  2. #2
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    Cool project. Keep us posted.

    I love that picture of the yellow Grandsport / 150 Promax - talk about a framer !!!!

    MDS

  3. #3
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    White and black Allison

    10 mpg is pretty impressive.

  4. #4
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    Good article.Good numbers too. Thx.

  5. #5
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    Cool project. Let me know if you need a driver. Ha!
    1995 Allison Grand Sport
    1998 Mercury Stock 2.5-260 SS

    1990 Velocity 30' - 502's

    Go Daddy Go! Racing

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  7. #6
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    that black and white GS is awesome!
    Allison XB02, 22ft Tritoon 225 4 stroke, two seadoo sparks

    Past rides 2001 STV EURO, Allison Grandsport, STV RiverRocket, STV Euro, STV ProComp, Hydrostream V-King
    RIP RPM RACING
    RIP GTS1

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  9. #7
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    Looks like I made a mistake in the article, when looking to order the upper mounts, the ProXS mounts are different, and stiffer than the SeaPro mounts.

  10. #8
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    So we have run our Grand Sport with a stock Merc 150 four stroke, and so far so good. We upgraded the upper mounts to the ProXS mounts, and they are a small improvement. Best was 72 MPH at 5570 RPM with a stock 28" promax prop. We need low water pickup to get it higher, and can probably squeeze a couple more out of it. That's our first step. Will look at solid mounts, and ECU upgrade after. The goal is 80 MPH with minimal modification.




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  12. #9
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    Quote Originally Posted by WavetoWave View Post
    Best was 72 MPH at 5570 RPM with a stock 28" promax prop.
    Was this a different run than the article? If so, you went up almost 200 rpm's but didn't increase the speed. Anything else change besides the mounts?

    How much setback does that hydraulic plate provide? And do you know where you are height wise with the stock case? Engine height makes a huge difference on these boats, so if you cone the case with lwp, it should make quite a difference. Have you tried any 3-blade props yet?

    Good luck!
    1995 Allison Grand Sport
    1998 Mercury Stock 2.5-260 SS

    1990 Velocity 30' - 502's

    Go Daddy Go! Racing

  13. #10
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    Quote Originally Posted by Ziemer View Post
    Was this a different run than the article? If so, you went up almost 200 rpm's but didn't increase the speed. Anything else change besides the mounts?

    How much setback does that hydraulic plate provide? And do you know where you are height wise with the stock case? Engine height makes a huge difference on these boats, so if you cone the case with lwp, it should make quite a difference. Have you tried any 3-blade props yet?

    Good luck!
    The only other difference was the prop. The first run was Darris' prop, a modified Promax he had laying around. This one was mine, stock promax.
    The Allison plate is 5.5, and we have 2.5 spacer. That run was about 1" below, maybe 1 1/4 if I remember correctly. Water pressure was dropping though, so didn't want to push it. I am doing the lower first, but I'm not with the boat right now, so it will have to be in January probably.

    Hoping to get my Trophy on it to try before I pull the lower unit off.

  14. #11
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    With your motor that low you might get close to your goal by just raising the motor. I went from 5/8 below to a 1/8 above the pad and saw a nice increase when I was playing with setups on mine

  15. #12
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    Quote Originally Posted by Honda92 View Post
    With your motor that low you might get close to your goal by just raising the motor. I went from 5/8 below to a 1/8 above the pad and saw a nice increase when I was playing with setups on mine
    Ya, definitely. Just being mindful of the water pressure right now. Especially the Promax prop, likes to be really high.

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