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  1. #1
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    Bad Regulator?? Volt Meter reading low.

    Maybe I’m thinking I have a problem when I really don’t. Dunno.
    Is it possible the regulator is going bad? Or something else?

    2003 Mercury 125 ELPTO #0T745549 (Tracker motor)

    Out on the water today….(3rd time the boat has been in the water this spring) and I noticed my volt meter was sitting at a somewhat lower level than 12V. Regardless of engine RPM the gauge needle never moves off this point ….see picture. I’m thinking it used to go up to about 13 volts.

    Tachometer is working fine.
    New voltage regulator in August of 2021 OEM Merc

    Starting battery is in good shape but seems to take longer to charge than the trolling motor batteries. Just the opposite of what the usual charging is.

    Battery showed 12+ volts on a digital meter when I got home.

    Right after the battery was charged this evening a digital volt meter showed 13.3 at the battery and the gauge on the dash showed (what I think) would be 12 volts. (the line just to the left of the 13 on the gauge in the attached picture)

    The dash gauge shows a little over 13 when the battery is on the charger.

    My son-in-law did install the starting battery for me a few weeks ago (bad shoulder kept me from lifting that high) he said he did accidently hooked the cables up backwards briefly. Nothing was switched on.

    Current regulator/rectifier physically looks fine.

    Any ideas? Or am I just thinking I have a problem when in all actuality I don't.
    Thanks!

    volt meter.jpg
    Last edited by WisconsinF; 03-16-2023 at 05:58 AM.

  2. Member
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    #2
    theres an ohm test for these regulators outlined in serv manual test batt voltage with a hand held digital volt meter with engine running should come up around 14.5 , would have batt tested also
    .................................................. ...the scariest thing in life is the unknown ...................................

  3. Member
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    #3
    ***UPDATE***
    Just for giggles I thought I'd dig a little deeper into what I thought was a charging problem.
    Found this (see pic) ....blown 25 amp mini fuse related to the regulator/rectifier.
    Would accidently hooking up the starting battery wrong (pos to neg / neg to pos just for a split second...thanks Brian!) cause this?

    Ignore second picture....I circled the wrong fuse holder...actually the one just to the left.
    Attached Images Attached Images
    Last edited by WisconsinF; 03-19-2023 at 06:55 AM. Reason: wrong pic

  4. Member
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    #4
    yea thatll do it
    .................................................. ...the scariest thing in life is the unknown ...................................

  5. Member
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    #5
    Quote Originally Posted by JOE54 View Post
    yea that'll do it
    Thanks Joe!! Going to do my own battery connections from now on

  6. Member
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    #6
    smart man indeed
    .................................................. ...the scariest thing in life is the unknown ...................................

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #7
    Only takes a microsecond to pop that fuse (or the larger ones used on bigger engine models).


    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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    #8
    Follow up….on the water today. All good. Volt meter reading good strong voltage and battery is charging correctly.

  9. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #9
    Quote Originally Posted by EuropeanAM View Post
    Only takes a microsecond to pop that fuse (or the larger ones used on bigger engine models).
    You can't even get the bad words out before it blows
    If you have integrity, nothing else matters. If you don't have integrity,
    nothing else matters.​

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    #10
    Quote Originally Posted by WisconsinF View Post
    Follow up….on the water today. All good. Volt meter reading good strong voltage and battery is charging correctly.
    .................................................. ...the scariest thing in life is the unknown ...................................