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  1. 07-09-2022, 03:18 PM #1
    Fish Boy
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    Merc 250 pro xs rough idle

    SN 2b534500

    2018 optimax pro xs

    Started having a rough idle yesterday so pulled plugs and all 3 on port were very fouled with soot. All 3 on starboard had normal wear.

    Unfortunately the lakes I guide on nearly daily have A LOT of idle zones so much of my time running big engine is at idle speeds.

    I started noticing a non burnt fuel smell at idle when I was down wind as well.

    Anything I should check on my own besides just replacing plugs and giving her a go?
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  2. SilverFox579
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    #2 07-10-2022, 07:51 AM
    The idle time is the problem and nothing you can do to correct that if in idle zones. I would confirm both thermostats are clean and working correctly and, if you're putting more than 100hrs on a set of plugs in a year's time, change them every 100hrs.
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  3. JOE54
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    #3 07-10-2022, 11:55 AM
    pull the stbd side rail away from head leaving direct inj in head key on look for any fuel dripping from rail , check tracker valve diaphram
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  4. EuropeanAM
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    #4 07-12-2022, 03:25 PM
    +1... above suggestions are all good places to start.


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  5. Fish Boy
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    #5 07-12-2022, 11:20 PM
    I replaced plugs and definitely runs better but still a terrible idle. Did a few hot laps around the lake to burn anything up and runs great on plane and gets on plane like normal but still terrible idle. No codes being thrown just running like a old 2.5 efi on a cold morning at idle.
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  6. JOE54
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    #6 07-13-2022, 07:29 AM
    Quote Originally Posted by EuropeanAM View Post
    +1... above suggestions are all good places to start.
    results ??????? yet
    .................................................. ...the scariest thing in life is the unknown ...................................
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  7. Macsimus
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    #7 07-15-2022, 09:06 AM
    If it was too much idle time, why wouldn't that affect the starboard plugs?
    There was a time that I didn't fish but I cannot remember it.

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  8. Fish Boy
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    #8 07-16-2022, 12:49 AM
    Quote Originally Posted by JOE54 View Post
    results ??????? yet
    Haven't been home much and now away for a wedding. I'll be back on the water all this coming week.
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