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  1. #1
    Join Date
    Feb 2020
    Bloomingdale il

    Half throttle power lose

    1997 200 mariner magnum efi runs and idles fine just at half throttle it's like a dead spot.runs great at full throttle

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
    Join Date
    Apr 2008
    Greenville, SC (US)
    If you would, please see the Announcements at the top of the Forum, and provide the Required Info (serial number). Thanks!

    Good idea to check the BASICS (Compression, Spark, Fuel Quality, Delivery and Pressure), perform a sweep-test of the TPI, and if no problems are found- check the Trigger (resistance tests, while slowly advancing throttle from idle to WOT position and back). Sometimes a "break" develops in the trigger harness that presents in only one position of the throttle.

    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 44 years (learn something new every day).
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