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  1. #1

    Default Yamaha YEMS 4.3 sterndrive

    Hi,

    I have a yamaha sterndrive engine that won't rev past 2500rpm. If I connect the to plugs to "lock" ignition I can rev it but is very tired.

    I think it is something electric.

    Does yamaha have something that keeps it from reving? I had a Yamaha Banshe quad years ago with a safety feature that stopped ignition if throttle was open and twist gas wasnt.

    Can anyone please point me in the right direction

  2. #2
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,853

    Default Re: Yamaha YEMS 4.3 sterndrive

    I have a yamaha sterndrive engine that won't rev past 2500rpm. If I connect the to plugs to "lock" ignition I can rev it but is very tired.
    Huh,..??..??

    Check the contents of the fuel filter for anything but clean fresh gasoline,.....
    Any Grease is Better,... Than No grease at All....

  3. #3
    Join Date
    Mar 2019
    Location
    Ottawa Canada
    Posts
    519

    Default Re: Yamaha YEMS 4.3 sterndrive

    Do a compression test.

  4. #4

    Default Re: Yamaha YEMS 4.3 sterndrive

    Compression is 10kg/150psi on all cylinders.

    Carburetor is refurbished a month ago.

    Is there something that tells ignition to advancr? When plug 13 and 14 is connected I can rev it higher, and if I turn the ignition and throttle the same time, it revs like never before.

    Sorry for my bad english, I'm from Sweden ��

  5. #5

    Default Re: Yamaha YEMS 4.3 sterndrive

    https://youtu.be/kT9LAvorgXA

    Video of how it runs

  6. #6

    Default Re: Yamaha YEMS 4.3 sterndrive

    Haven't anyone fiddled with these motors?

  7. #7

    Default Re: Yamaha YEMS 4.3 sterndrive

    Quote Originally Posted by Malmsten View Post
    Haven't anyone fiddled with these motors?
    Yamaha only offered those stern drives in the U.S. for a couple years. Thay were sued for patent infringement & that was that. I watched your vid, sounds like a fuel problem.

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