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  1. #1

    Am I missing something here? Low

    Ok well long story short, my mods are listed below. I took te ski out for the first time today just to do a little test, and to be honest was disappointed. In almost flat calm water, 6" or less chop, had a best speed of 61.4 mph gps'd w/ a full tank of gas. Porpising was unreal! Could not keep the ski In the water what so ever, messed with the trim, hardly any help.

    As far as I've researched, with these mods, should be cclose to 70 mph ski correct? I had the Riva efi controll unit. Didn't think I needed it but what do y'all think? I'll pull the plugs tommorrow and pos pics

    Any tips on what might be going on would be appreciated!


    Ps - tach is still in the Mail so no Rpm #s yet


  2. #2
    "just sayin".. jetdave56's Avatar
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    On the porpoising where's the trim...usually neutral works best for less bouncing..

  3. #3
    "just sayin".. jetdave56's Avatar
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    Well first yes you need to see how many RPMs your spinning to see if your in the normal range (7000-7200)..then your gps on a 1/4 tank would be 63mph...about normal for stock engine...none of your mods increase RPMs and your prop which should give a good holeshot and midrange but nothing on top...is Jim's plate adjusted for flat water speed with washers..lots info on plate adjustment...grate and shoe seal and JW give you better hook up and acceleration..but does not necessarily mean high #s..IMHO

  4. #4
    Matt Hill's Avatar
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    You're going to need to work on your ride plate angle to get that thing to stop porpoising. I spent quite a bit of time testing last summer. I would make a couple passes and pull the boat out of the water and make adjustments and test some more. The more you play with your setup the more you learn how to get it to lay down the number and keep the hull on a smooth plane. Toward the end of my few weeks at the lakehouse I was working with the trim tabs and playing with those along with the sponsons and learned quite a bit. You will find that thousandths of an inch make a big difference. Once you get the ski to settle down you'll be able to ride it out and get more speed out of it. Then once you get your tach you can start working on prop pitch and so forth. But you've got to get that hull dialed in first.

  5. #5
    Thanks guys, nothing on the hull (tabs, rideplate, etc) is adjusted with washers, its all in stock place. What kind of washers would you reccomend?

    So what mods can I do to increse RPM? Ive searched numerous times on the site about speed mods, and am still confused.

    I played with the trim, and tried it in every position. The thing just keeps on bouncing

  6. #6
    "just sayin".. jetdave56's Avatar
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    Quote Originally Posted by SkiBoy720 View Post
    Thanks guys, nothing on the hull (tabs, rideplate, etc) is adjusted with washers, its all in stock place. What kind of washers would you reccomend?

    So what mods can I do to increse RPM? Ive searched numerous times on the site about speed mods, and am still confused.

    I played with the trim, and tried it in every position. The thing just keeps on bouncing
    For more power, RPMs and to bring you to your goal of 70mph...you need the best 1-2 punch for a 2 stroke...higher compression and porting...its not cheap about $1000 But you will have a whole different ski!!...its the best answer to the more advanced SC skis...

    Like in the previous post by Matt, you need "trial and error" with those thin washers under the bolts...many GPR gurus go by the theory to raise the back of the plate (only very thin washers)and thicker washers in the front..that will drop the front of the plate and raise the back...BUT the front NOT low enough to be below the pump shoe or hull..

    I had bad bounce like you...couldn't settle her down...I brought the ride plate and tabs down 0.060 all around with my Jim plate giving less front to back angle...if I lost top speed I gained back with less bouncing and better holeshot...but it works better in different ways for riders preference...G/L

  7. #7
    Well I'd thought I'd update this thread invade anyone was having the same problems I was. Did a little work this week, and boy did I pay off. Ended up putting 2 thin washers under each trim tab bolt, and one washer under each back ride plate bolt. Could do a little more fine tuning, she stays planted now, but when I hit a wake or wave, it bounces 5-8 times before it settles down.

    In 55* water, 68* air temp, light chop (8" or less) had a best speed of 67.5 mph on a 1/4 tank of fuel. No superman, just sitting on the back of the seat


  8. #8
    Banned User
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    You should be able to hit 70 mph with all of hose mods! What's the impression like and how's the wear ring? Running premix? If so what ratio?

  9. #9
    See that's what I thought! Compression I will have I test again this week, will report back on that. Wear ring looked good when I installed the impellor, I'll post a pic. Guys on here said it wasn't bad and that I didn't need to replace
    It. And no pre-mix yet, was gonna wait til I built the motor next winter.

    Any other tips for me?




  10. #10
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    Should have only about a 1/16" all the way round ring /prop. How's the prop leading edges? Wear ring looks a little worn but nothing crazy

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