Thread: low rpm surge

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  1. #1
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    low rpm surge

    serial number-0t512962
    2002 225 optimax. 31 hours on new powerhead. 416 total hours
    Picked up a 2002 stratos 21xl magnum about 6 months ago with a 2002 225 optimax "my first merc" I have noticed at an idle it seems to be running a little rough at low rpms once I'm up on plain and moving you can notice anything at all runs great all the way up too 5700rpms where I'm getting 70.86 on gps with a 25p tempest. Curious if its a fuel issue seeing as in las vegas I have yet to find any ethanol free fuel. also I have been running 91 with merc quick clean every other tank with merc optimax oil. After doing some reading I am not so sure the 91 is such a great idea. Any ideas as to what could be going on.

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  3. Member
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    #2
    Change it back to 87 octane the 91 will just carbon it up.

  4. Member
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    #3
    I would check/change the sparkplugs and replace the fuel filter for starters....
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  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    +1 to both of the above comments- then see how it does.


    Dual Mercury Master Technician- for Mercury Outboards, Racing & Mercruiser Sterndrives in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 39 years (learn something new every day).
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  6. Member
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    #5
    Also you should be running quikleen every tank.

  7. Member
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    #6
    Thank you guys will fill it up with 87 from now on and also start running quikleen every tank will update after my next few trips on the lake. also replaced the fuel filter checked plugs and they seem fine not burned or fouled at all all gaped correctly

  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #7
    Make sure you're using NGK: IZFR5G, gapped at .032-.033" (ONLY). Torque plugs to 20 lbs/ft with a torque wrench.


    Dual Mercury Master Technician- for Mercury Outboards, Racing & Mercruiser Sterndrives in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 39 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

  9. Member
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    #8
    Make sure when gapping your new plugs to only use a wire gauge gapper, not the round friction slide type or feeler gauge type. To keep fuel fresh between outings, you should also be using Quickare every time you refuel. See this post - Oil, Battery, Spark Plugs, Fuel and Fuel Additive Recommendations
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax