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  1. #1
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    Mercury 150 four stroke spark plug problem

    I have a 2015 mercury 150 four stroke with 185 hours on it .
    serial number: 2B130092
    I live up near Buffalo NY and yesterday I was winterizing the motor . Removed spark plugs to fog the cylinders and noticed the plugs are black and sooty . I attached some pictures. This is the fifth summer I have used the boat and previous times I winterized it the plugs were the normal tan color. I run only non ethanol fuel , also when I removed the prop to drain lower gear case lube the inside of the prop and the washer and nut had that heavy sooty black stuff on it as well . Any idea what could be causing my issues. Plugs were replaced spring of 2019 so two summers on them . Could it be because I fog the cylinders ? Thanks for your help . I bought the Mercury service manual from Don and there is really nothing in it to troubleshoot the plugs .I use Mercury 4 stroke synthetic blend 25w-40 oil since new .
    Jim Kaz
    kaz89@verizon.net
    Attached Images Attached Images

  2. Member
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    May 2011
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    #2
    What octane fuel are you running and how much time do you spend at idle/lower rpms?
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


  3. Member
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    #3
    90 octane rec fuel ethanol free fuel
    not much at idle only in and out of the marinas

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    Greenville, SC (US)
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    #4
    Quote Originally Posted by Kazusmc View Post
    90 octane rec fuel ethanol free fuel
    Above quote is a likely contributor. 87 Octane would be preferable as it is what the engine was calibrated to run.

    Are you running Quickleen and Quickare in your fuel?

    Are both engines coming up to operating temps at idle (as monitored on a Smartcraft Instrument)?


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

  5. Member
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    #5
    Sorry for confusion, pictures are of same plugs just rotated them for second picture
    yes I use the quick care and quick clean every time I fill up
    we only have 90 octane rec fuel up near Buffalo NY
    I can only get 87 octane with ethanol in it , I’ve always been Leary of using it
    the motor ran perfect all summer never any problems or warning alarms

  6. Member
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    MO
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    #6
    Is there a lot of idle time on these plugs?

  7. Member
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    Nov 2019
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    Moyock, NC
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    #7
    He said only in / out of the marina.

    Don't worry about 87 ethanol gas. Just get it at a station that sees a good amount of traffic.
    MY Engine Serial Number : 2B411498


  8. Member
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    Aug 2007
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    MO
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    #8
    Missed the idling part. How hard does it get ran? Is it getting any good hard runs on it?

  9. Member
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    #9
    Quote Originally Posted by moymurfs View Post
    Don't worry about 87 ethanol gas. Just get it at a station that sees a good amount of traffic.
    +1!
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


  10. Member
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    Nov 2017
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    West Seneca New York
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    #10
    No problems running the ethanol 87 fuel then ??

  11. Member
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    #11
    No.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax