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  1. #1
    Member
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    Sep 2013
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    St. Charles, MO
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    Mystery warning tone Merc. 150 four stroke

    Merc. 150 four stroke, serial # 2B602906 has a mystery warning tone? I am receiving a constant warning tone after about 10 seconds of running at 4500 RPM or above whether I'm trimmed up or not.
    Outboard is getting plenty of water and has a brand new impeller and oil.
    Cooling discharge is not hot, it's like the river water temp I'm running in. Motor has yet to go into Guardian mode and tone instantly stops if I throttle back to 3500 RPM or lower.
    Any insight is greatly appreciated.

    Thank you,

  2. Member
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    May 2011
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    Spangle, WA
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    #2
    Need to have codes read - WARNING HORN "BEEPED"

    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


  3. Member
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    #3
    Thanks!

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    Apr 2008
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    Greenville, SC (US)
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    #4
    Odds are fairly high that it actually HAS been in Guardian (you just recognized it as a warning horn).

    Get the Run History and Freeze Frame (Fault) History read on the G3 Diagnostic System for best results.


    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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  5. Member
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    #5
    Thank you for the diagnostic direction, wish you guys we're in my back yard!

  6. Member Extremeboating's Avatar
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    May 2021
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    Concord, CA
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    484
    #6
    If the water is not peeing out water that's warmer than the actual river temperature then the chances are pretty good that you have a bad t-stat and the engine does not like that. Getting codes is definitely a great first step to go, but don't be surprised if it does indicate a code regarding thermostat or something involving the cooling system.

    I'm just going off of what you indicated here. I am in no way suggesting you replace anything before you do the necessary diagnostic steps required to arrive to that point. Just want to be clear about that. Lol.
    Last edited by Extremeboating; 06-29-2021 at 12:43 AM.
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  7. Member
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    May 2011
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    Spangle, WA
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    #7
    There are numerous things that can cause one of two alarm strategies, solid tone or beep pattern. You can toss things at the engine hoping to solve the problem, spend $600+ for a scanner to do your own diagnostics, or take to a dealer with the Mercury diagnostic system and have them printout reports with engine data, current active faults, and fault history so you know where to start.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax