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  1. #1
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    1999 50hp Auto-start issues

    Let me preface by saying that, although I was Johnrude Master Tech and Merc certified in the past, I know little about 4 strokes. I've been out of the business for 15 years, but still do a little work on the side from time to time, primarily (and successfully) on 2 strokes.

    I took in a carb job on a '99 50hp Bigfoot. I quickly remembered why I don't like 4 strokes LOL. Anyhoo, got the carbs cleaned, rebuilt, and reinstalled...but the Auto-Start seems to be giving me issues. My strategy was to get the mixture needles close, sync the plates, and then fine tune the mixture. However, as the engine comes up to operating temp, it wants to race out of control.

    Can anyone explain how the Auto-start works, what drives it, and what constitutes a problem with it. It could even be that my sync and link is just so far out of whack that that is my primary issue. I should have access to a service manual, but not until the first of next week.

    Any guidance will be greatly appreciated.

    Edit: The mixture needle covers were in place when I started. The #1 needle was right at 2 turns out, but the other three were screwed all the way in. That doesn't seem right at all.
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  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    What's the engine serial number?


    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).
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  3. Member
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    #3
    0G796587
    1992 Ranger 690
    1991 Johnson 150 Fastrike
    2014 Minn Kota Terrova 112 w/i-Pilot Link
    (Coming Soon) Humminbird Helix 10 Mega SI GPS G2N
    Humminbird Helix 7 DI GPS G2N
    Helix 5 DI

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    Service Manual 828631R3 has Synchronization and Setup instructions beginning on page 3B-12. All of the idle air mixture screws must be at 2.5 turns out before you begin synchronizing with the Vacuumate tool.

    ALL steps must be performed precisely.

    Watch the cam-arm as it is sometimes improperly oriented during assembly (resulting in carb linkage binding).


    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
    Thank you!
    1992 Ranger 690
    1991 Johnson 150 Fastrike
    2014 Minn Kota Terrova 112 w/i-Pilot Link
    (Coming Soon) Humminbird Helix 10 Mega SI GPS G2N
    Humminbird Helix 7 DI GPS G2N
    Helix 5 DI