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  1. 07-31-2021, 05:36 PM #1
    broncob
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    200 efi only runs good while trimming

    i have a 1998 mercury 200 efi on triton boat. motor will only run at full rpm when i am holding trim either up or down. boat will hardly plane out but when you hit trim up it take off full rpm. have checked grounds and changed stator and voltage regulators. bypassed all modules with no luck. any help or thoughts would be much appreciated.
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  2. leonreno
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    #2 07-31-2021, 11:03 PM
    Off hand sounds like could be a ground problem, maybe long shot but could be a problem with ECM that the trim activation is “fixing” by providing a ground path. If you can get a known good ecm to test on your motor I would do that. Also make sure you do not have an over voltage problem too.
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  3. broncob
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    #3 08-02-2021, 09:56 PM
    I have located a known good ecu so I will give it a try
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  4. JOE54
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    #4 08-03-2021, 07:01 AM
    what is batt voltage while underway / no more than 14.5
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  5. broncob
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    #5 08-03-2021, 10:11 PM
    yes i checked voltage and it was 14.5 but i had spare stator and regulators and changed them anyway. did not help
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  6. EuropeanAM
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    #6 08-04-2021, 06:22 PM
    Two items to try:

    1. Transom Mounted (test) keyswitch harness (eliminating the boat side of the wiring). Won't have trim but you'll know if it will run right without trim this way.

    2. Monitor FUEL PRESSURE with a gauge, when it won't accelerate and when you operate trim and it WILL accelerate. ANY difference in readings (and what were they)?


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  7. Wildcat82
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    #7 08-16-2021, 05:18 PM
    Quote Originally Posted by JOE54 View Post
    what is batt voltage while underway / no more than 14.5
    Are you having any luck fixing this issue? My motor is doing the exact same thing and I have a post on this as well. Curious to know if you have resolved this gremlin.
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  8. Wildride58
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    #8 08-16-2021, 06:40 PM
    +1, mine went pretty much away for awhile. Fishing Saturday it was back and very noticeable when I hit the trim. Watching.
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