Zamco JetLark - 650 Yamaha Conversion
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  1. #1
    PWCToday Guru Ol' Reliable 550's Avatar
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    Zamco JetLark - 650 Yamaha Conversion

    So I picked up this old school JetLark mini boat from a guy in my community for a $1 and a case of beer.
    I've never seen one of these before and didn't know much about them.
    The original owner didn't even know what it was called until I did a little research on it.



    The boat had an original 440 Kawasaki engine in it, and a Berkley Pump. The outside of the boat was in rough shape, but it did come complete with seats which the owner upholstered himself. The 440 engine actually fired up, but immediately began to run away. After a complete tear down, I realized the crank seals where bad and would need to be replaced. With my little experience with Kawi engines, I figured why not drop in a Yamaha 650 out of my old Superjet. I used a RHAAS conversion coupler on the JetLark shaft, unfortunately I stripped the original coupler and needed to get it rethreaded at a machine shop.



    The the 650 Yamaha bolted up to the aluminum engine plate after I drilled some holes to match up with the engine case bolts.
    I used a spare gas tank from a old waverunner since the old one cracked.



    Now the tough part was trying to find a way to mod the exhaust. Unfortunately the Yamaha "Bread box"
    was too long, the seats would not be able to fold all the way back. I was in the market for a Coffman manifold/ Factory Manifold,
    but finding one of those used at a budget price has been difficult. I decided to take matters in my own hands and cut the stock manifold in half,
    grind down the pipe and connect a stock 650sx pipe via a rubber coupler.

    photo hosting

    image hosting gif

    As for the ignition switch, I used a 2 Momentary Key Switch I found off Amazon, spliced the 4 wires so when you turn to the right,
    it would turn the engine on, and to the left, it would kill the engine. I works great. Not bad for $15.



    I also installed a boat toggle panel for my bilge pump and navigation lights and in the future a stereo system (fingers crossed!)
    And I made a wooden hatch with a piano hinge that I plan on turfing soon.




    The boat idled great when I tested it, however it bogged when I hit full throttle.
    The SBN mikuni carb settings were 120 pilot and 115 main jet for the stock Superjet.
    rejetted the main jet to a 135 after reading on here that that is standard if using a 650 and a cheater pipe.
    However, I'm waiting on better weather to do another test run and see if I can tune it. Any carb advice would be great!


    img

    i
    1993 701 SuperJet - PATRIOT SKI
    1994 Yamaha Waveblaster 2nd Owner
    1986 Kawasaki JS550 - Yamasaki 650 Conversion
    1987 Kawasaki 300sx - Group K Mod, sunk and locked. Used as beer cooler.
    1990 Kawi 550sx
    - "Ol' Reliable." Caught on fire, sunk, whereabouts UNKNOWN.
    JetLark Mini Boat - Build Thread
    Ultranautics JetStar - 60hp

  2. #2
    Resident Guru mmcahow's Avatar
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    Re: Zamco JetLark - 650 Yamaha Conversion

    That's frickin awesome!

  3. #3
    PWCToday.com Is My Home Away From Home
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    Re: Zamco JetLark - 650 Yamaha Conversion

    Cool project, should be a fun boat.

    I've never seen reverse jetting for a stock engine. I believe 115/135 is stock for a 650. I would stay 115 on the low and 137.5 on the high. Looks like a plumbing coupler on mani to pipe (purple sticker). Thoes dont last long around high heat. I would also put a warter shut off on head pipe warter in so you can fine tune it. Cheater piped make power when you dry the out, just like any other pipe. Good thinking on making the pipe work for your set up.

    Keep us posted on ur progress!

  4. #4
    Resident Guru rock_smasher's Avatar
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    Re: Zamco JetLark - 650 Yamaha Conversion

    That is very cool! I have a similar boat, will be converting to jet drive someday- WR3 pump section and pump, kawi 750 motor. Great find!
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    Those who will beat their swords into plows, will plow for those who do not.

    I got 99 sockets but a 10mm aint one

  5. #5
    PWCToday Guru Ol' Reliable 550's Avatar
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    Re: Zamco JetLark - 650 Yamaha Conversion

    Driftmaster,

    Thanks for the advice. I will be in the market for a silcone turbo coupler that can withstand the heat. As for the cooling line shut off, are you talking about a butterfly valve to reduce the amount of water that flows to the pipe?
    1993 701 SuperJet - PATRIOT SKI
    1994 Yamaha Waveblaster 2nd Owner
    1986 Kawasaki JS550 - Yamasaki 650 Conversion
    1987 Kawasaki 300sx - Group K Mod, sunk and locked. Used as beer cooler.
    1990 Kawi 550sx
    - "Ol' Reliable." Caught on fire, sunk, whereabouts UNKNOWN.
    JetLark Mini Boat - Build Thread
    Ultranautics JetStar - 60hp

  6. #6
    PWCToday.com Is My Home Away From Home
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    Re: Zamco JetLark - 650 Yamaha Conversion

    Yeah man no problem, always glad to give some advice when I can... I like a little more lee way than the butterfly valves 1/4 turn, but that will work, just dont bump it. You can find screw type at any hardware store.

  7. #7
    Resident Guru rock_smasher's Avatar
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    Re: Zamco JetLark - 650 Yamaha Conversion

    The coupler hose can be found at big truck shops, Kenworth, Peterbilt, most heavy duty repair shops have it, but it's expensive.
    Those who will beat their swords into plows, will plow for those who do not.

    I got 99 sockets but a 10mm aint one

  8. #8
    PWCToday.com Is My Home Away From Home
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    Re: Zamco JetLark - 650 Yamaha Conversion

    I also ment to say turn the warter down till the pipe will steem warter drops when driped on the pipe. Its a fine line between steem and scalding.

    keep us posted! This is the first build I've been interested in in a long time. I love a back yard budget builds.
    Anybody can build with money, the mind is another story.

  9. #9
    PWCToday.com Is My Home Away From Home fox river pwc's Avatar
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    Re: Zamco JetLark - 650 Yamaha Conversion

    Reverse jetting was always oem standard on 650 yamis.

    Bring that beast up by me in waterford, wi and we'll get it tuned perfectly. I have a private launch and the perfect spot for tuning + I stock a few thousand mikuni jets/springs/n&s.


    WHEN IN DOUBT, GAS IT!

    Yeah, I'm an @sshole, but I'm not a complete @sshole.

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  10. #10
    Top Dog orangefinger's Avatar
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    Re: Zamco JetLark - 650 Yamaha Conversion

    awesome Frankenstein, love those projects !!
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