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  1. #1
    Join Date
    Aug 2004
    Location
    A tiny Island, Caribbean
    Posts
    16,756

    Question Yamaha outboard shuddering

    I have two 85hp 2-stroke Yamaha outboards.

    One 'shudders' from time to time, then seems to 'clear' the problem' - reduce throttle/turn off and restart and - then runs OK.

    Both linked to the same fuel tank.

    Any suggestions as to the cause.
    RELAX, Rum may not be the answer, but nor is water or juice. Now what is your Question?

  2. #2
    Join Date
    May 2001
    Posts
    15,477

    Default Re: Yamaha outboard shuddering

    Blocked jet(s), faulty spark plug?

  3. #3
    Join Date
    Jun 2004
    Location
    Anglesey Wales
    Posts
    11,121

    Default Re: Yamaha outboard shuddering

    Yep LJ, that’s where I’d start
    Jerk of all Trades Master of None

  4. #4
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,553

    Default Re: Yamaha outboard shuddering

    Quote Originally Posted by Rum_Pirate View Post
    I have two 85hp 2-stroke Yamaha outboards.

    One 'shudders' from time to time, then seems to 'clear' the problem' - reduce throttle/turn off and restart and - then runs OK.

    Both linked to the same fuel tank.

    Any suggestions as to the cause.
    Dropping one cylinder ??

    As suggested spark plugs are first check......... could try swapping them with the plugs in the other engine.

    Ht leads ??? Coils ?? Defective CDI possible

    Info on diagnostic testing in the CDI Electronics Troubleshooting Guide http://www.cdielectronics.com/troubleshootingguide/

  5. #5
    Join Date
    Aug 2004
    Location
    A tiny Island, Caribbean
    Posts
    16,756

    Default Re: Yamaha outboard shuddering

    Quote Originally Posted by longjohnsilver View Post
    Blocked jet(s), faulty spark plug?
    Thanks.

    I have changed and re-gapped the spark plugs.

    I will remove and clean the carbs(jets).

    When shutting down I disconnect the fuel line and let the engine use up the fuel in the line.
    However this probably does not empty the carbs or jets.
    RELAX, Rum may not be the answer, but nor is water or juice. Now what is your Question?

  6. #6
    Join Date
    Aug 2004
    Location
    A tiny Island, Caribbean
    Posts
    16,756

    Default Re: Yamaha outboard shuddering

    Quote Originally Posted by VicS View Post
    Dropping one cylinder ??

    As suggested spark plugs are first check......... could try swapping them with the plugs in the other engine.

    Ht leads ??? Coils ?? Defective CDI possible

    Info on diagnostic testing in the CDI Electronics Troubleshooting Guide http://www.cdielectronics.com/troubleshootingguide/
    Appreciated. will follow up.
    RELAX, Rum may not be the answer, but nor is water or juice. Now what is your Question?

  7. #7
    Join Date
    Mar 2009
    Location
    Tasmania, Australia
    Posts
    4,266

    Default Re: Yamaha outboard shuddering

    Quote Originally Posted by Rum_Pirate View Post
    ......When shutting down I disconnect the fuel line and let the engine use up the fuel in the line.
    However this probably does not empty the carbs or jets.
    The procedure (running engine until it stops) you are following is what is recommended to eliminate residual oil blocking jets and gumming up carb bowls. I always do this with any two stroke on shut down also.
    Last edited by AndieMac; 20-08-19 at 23:17.

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