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  1. #1
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    New Adjust-A-Thrust and Reeds

    I figured since there aren't really any good threads on the Adjust-A-Thrust, I would start this one and document my tuning and results. I guess there are a few out there but nobody has really described how it performs and if it was worth it to them or not. I also ask anyone to give tips or their results as well on their AAT.

    I've also had a problem with my boat not really hitting hard out of the hole, a weak mid-range, as well as very difficult starting. Really the only thing I can think of is the reeds. I have V-Force Delta 2's on my boat and there is some gap under the petals so I think it might be time to change them out. I've had this boat since 2008 and have not ever replaced them so it is time. Plus my FA's are a little oil soaked so I guess I'm getting some back flow through the carbs because the reeds are old.

    I will be able to get on the water come 4th of July weekend so it's gonna be a little bit before I get things underway.
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  2. #2
    Banned User
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    I have 2 of AATs as well to install and test out. One on a Pro 1200 and the other on my X45. I will share my results as well.

  3. #3
    LaveyT's Avatar
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    Thats a pretty cool looking product. A machinist's dream really to design, patent, manufacture and sell your own product. I make Velocity stacks and solid motor mounts for OMC go fast guys, but only because the original suppliers quit manufacturing them years ago. I make a run of Velocity stacks and they will last a couple of years. I will never make up the money I have spent on boating Looking forward to the results, I used maker buoys at the Dam for base line acceleration prop testing on the Lavey. A stop watch in one hand Do you guys have a more sophisticated way to do your testing?

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by hyoctane23 View Post
    ... not really hitting hard out of the hole, a weak mid-range...
    One item that is easy to dismiss or overlook is sealing of the jet pump itself, forward of the impeller. This includes the metal joint between the wear ring surrounding the impeller (aka the extension ring) and the jet pump base.

    WeberPower sells a 'gasket' (part number 403454) that looks like it could be retro fitted to the Polaris jet pumps. I do not know if this requires machining a groove for the seal to seat into.

    The impeller creates a strong suction everywhere forward of the impeller blades, and the metal to metal seam of the pump sections can be a less than airtight mating. Any air leaks into the jet pump will ventilate the impeller and reduce acceleration thrust.

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  5. #5
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Hey K....not really cavitation at all. The engine doesn't have any power.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by hyoctane23 View Post
    Hey K....not really cavitation at all. The engine doesn't have any power.
    I know, but when you get the power back, then the jet pump needs to properly turn that power into water jet thrust.

    I was talking about jet pump ventilation, not cavitation. Similar symptoms from the rider's seat, but different causes and different fixes.

  7. #7

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    Quote Originally Posted by K447 View Post
    Quote Originally Posted by hyoctane23 View Post
    ... not really hitting hard out of the hole, a weak mid-range...
    One item that is easy to dismiss or overlook is sealing of the jet pump itself, forward of the impeller. This includes the metal joint between the wear ring surrounding the impeller (aka the extension ring) and the jet pump base.

    WeberPower sells a 'gasket' (part number 403454) that looks like it could be retro fitted to the Polaris jet pumps. I do not know if this requires machining a groove for the seal to seat into.

    The impeller creates a strong suction everywhere forward of the impeller blades, and the metal to metal seam of the pump sections can be a less than airtight mating. Any air leaks into the jet pump will ventilate the impeller and reduce acceleration thrust.

    Click image for larger version. 

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    i use grey permatex to seal the pump sections

  8. #8
    RizzO
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    I have the AAT on both my pro1200's and they do make a world of difference. They keep pump stuffed during take off. They are an easy install and very easy to change the shuttle size while in h2o. Brian I have 6 different size shuttles if you want to see what works bezt.

    Ruz

  9. #9
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Update: I replaced the reeds yesterday and got in the water today. Took some trial and error but the hit out of the hole is night and day from before with the old reeds.

    I have Polarisracer166's jetting in my boat by the way. I started with the lows 2 turns out and she was blubbering some after idling but I ended up right at 3/4 turns out like recommended. After getting the lows tuned, I tried to tune the highs. I'm about 1/16 turn out and still struggle to get 7600 RPM. I figured I would take the springs out of the valves to be sure they are opening all the way and they sure are.

    Another thing I did was turn the adjusters on the valves almost all the way in and holy crap what a difference. Before, they were barely turned in but I guess they were letting the valves open too soon...she hits really hard on the low end now.

    I'm not going to put the AAT in until I can get my RPMs up to at least 7850. I did notice I would gain about 100 RPMs if I let off the throttle a smidge....I think this means I'm rich? Any ideas what could be holding me back some? The wash on PTO and MAG are little nicks and the CEN is def a little rich with about a thumbnail sized wash.

  10. #10
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    I also should mention that starting is a LOT easier...

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