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  1. #1
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    Stator/ Regulator problem

    Have a 2002 90 ELPTO #OT481094. Starts fine, sometimes the tach will bounce around erratically while running. Going down the lake the RPM's will drop for a couple seconds, then pick back up. Doesn't seem to be missing, just a RPM drop and picks back up. What should I look at 1st.

    Thanks

  2. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #2
    Is the engine actually changing speed or just the tach?
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  3. Member
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    #3
    Quote Originally Posted by CatFan View Post
    Is the engine actually changing speed or just the tach?
    The boat will slow a bit, the RPM will randomly move up or down.

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    Check the voltage regulator for burnt, browned, blackened or "crispy" wiring and connectors (especially the RED and YELLOW wires).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #5
    Quote Originally Posted by EuropeanAM View Post
    Check the voltage regulator for burnt, browned, blackened or "crispy" wiring and connectors (especially the RED and YELLOW wires).
    They look fine. One thing I have noticed is that my starting battery takes a couple of hours to charge after I get home. It's only 4 months old.
    Last edited by Hydrasport80; 11-16-2021 at 02:02 PM.

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #6
    Clean cannon plug connector (disconnect, clean male pins, spread male pins SLIGHTLY, then reconnect and lock in place with factory supplied keeper).

    If problem persists, Isolate the tachometer (disconnect and isolate wiring)- see if the problem persists.

    And if still occurring, temporarily (for one very short run to diagnose) isolate the regulator as well.

    NOTE: "ISOLATE" meaning to "Disconnect and prevent connectors from touching other objects by means of an insulating material such as plastic, rubber, or electrical tape".


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #7
    Found a new Mercury OEM regulator on Ebay for $35 shipped. Most were listed between $220 to $169, appears the guy didn't know what he had. In the meantime, I'll check all the connections as suggested.

  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #8
    Very unlikely that's OEM... but hope it works out well for you.


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    #9
    Put the new regulator on and took it out today. The new regulator didn't help, same as before. Next step will be to isolate the tach as mentioned above. What is the reasoning behind doing this.

    Thanks

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #10
    Regulators can fail in several ways- in some cases, they can result in transient voltage or current passing to the ignition side of the system.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #11
    OK, since the regulator is new, should I isolate the tach? Is the tach the gray wire?

  12. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #12
    Tach is the gray wire. NEW does not necessarily mean "GOOD"... so I would DEFINITELY isolate the regulator to be certain.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #13
    Bringing this thread back up again. Looks like I have the same motor and same problem as "Crappie Bob" Since the last time I posted I have put new kits in the carbs and changed to a lead acid battery. Took it out today with the tach disconnected (gray wire) and had the same results. Motor would slow down and speed up while running on plane (probably running around 4000 rpm's). I haven't rebuilt the fuel pump which I think is my next step as the motor is 20 years old and it's never had it done. Still idles good and isn't missing at any rpm. Any thoughts.

  14. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #14
    Pulse fuel pump would be a good idea... as would the fuel filter, and verifying ALL Sync-n-Link Settings (required when you unbolt or loosen carbs).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #15
    Rebuilt the fuel pump and did the link and sync, fuel filter was replaced. Took it out this evening for a quick check. Motor started fine, idle was a bit high, ran smooth. Went down the lake and had the same problem, drop in rpm's and pick back up. fished a little and came back up the lake. Loosened the fuel cap to see if this would affect anything. Ran a little bit more rpm's than normal (about 4000) and it ran great, no drop in rpm's. Will go back to the lake in a day or two and run it a lot more and see what it does. Also the tack didn't jump around like it had been doing. One step closer.

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    #16
    Took it out again today, exactly the same as before, 4000 rpm's it runs great. Tach working fine. Going to leave it alone for now.

  17. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #17
    Sounds like the tach is steady now? If so, next time you're at the water check to see what RPM the problem first presents at (be as precise as possible).

    Also, double check your fuel line connections at the bulb and front of the engine. You may have a folded-over inner liner on the fuel line, which can cause a restriction.


    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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