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  1. #1

    Default 90 mercury rattle only when shutting off

    So I just purchased an 07 mako with a 90 Mercury. Motor seems to run fine with no issue. Except when I turn off the motor there is a rattle noise for just a moment. Sound like something is loose and when the motor turns off whatever is loose is no longer under load so it rattles as the motor comes to a complete stop. I’m a new boater and not sure what the rattle could be, if it’s just something loose or more serious or rather it’s safe to be out on the boat. Any assistance would be greatly appreciated.
    Rob
    Last edited by Rnewmans; 05-17-2020 at 10:48 AM.

  2. #2
    Join Date
    Sep 2010
    Posts
    19,433

    Default Re: 90 mercury rattle only when shutting off

    2 stroke or 4 stroke ?-----Serial #

  3. #3

    Default Re: 90 mercury rattle only when shutting off

    2-stroke not sure about serial #

  4. #4

    Default Re: 90 mercury rattle only when shutting off

    Sound like something is loose and when the motor turns off whatever is loose is no longer under load so it rattles as the motor comes to a complete stop.

  5. #5
    Join Date
    Sep 2010
    Posts
    19,433

    Default Re: 90 mercury rattle only when shutting off

    Check flywheel.----Can you move it up and down at all ?----Check flywheel nut torque.----Or on the port side of the motor you will find an exhaust cover ( 20 bolts or so ) to remove.----You can then inspect pistons / rings / connecting rod play.-----2 new gaskets if everything in there is OK.

  6. #6

    Default Re: 90 mercury rattle only when shutting off

    Quote Originally Posted by racerone View Post
    Check flywheel.----Can you move it up and down at all ?----Check flywheel nut torque.----Or on the port side of the motor you will find an exhaust cover ( 20 bolts or so ) to remove.----You can then inspect pistons / rings / connecting rod play.-----2 new gaskets if everything in there is OK.
    not at the boat currently but Iíll give that a try. Thanks.

  7. #7
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,355

    Default Re: 90 mercury rattle only when shutting off

    If your shutting it off in gear you are hearing clutch dog ratchet from prop turning. If in neutral have seen the lower bearing inner race separator bad..balls keep spinning in race when shut off. Seen this several times
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

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