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  1. #1
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    300xs with mad efi tunner question

    I put a mad efi tunner on my 300xs now motor bogs and wont come out of the whole what should be done to fix this issue. Motor is stock, put a cb foil on lower has 1.62 sporty I've tried promax, bravo, and performer props. Any good ideas would be appreciated

  2. Member
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    #2
    One good idea would be to put the serial number of your engine in your post

  3. Major Flagelator Gamblinman's Avatar
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    Jun 2004
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    #3
    With that MAD EFI tuner, you lost exhaust venting on the prop and therefore do not have the slip to allow the motor to rev into its power range for take-off. A smaller pitched prop may help, but then you lose speed on top end to compensate for the loss of performance on the bottom end. It's a catch 22 situation.
    "Better to remain silent and be thought a fool than to speak out and remove all doubt."

  4. Member
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    #4
    Pull out any plugs you may have in the prop.
    Jimmy
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  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!

    What boat is this engine on? What prop?

    Holeshot can be a bit tricky with that combination as it's lost the tuner length that helped in purging the water from the exhaust when the engine spooled up. SOME have had good luck with starting HIGH on their hydraulic jackplate and dropping it down as they accelerate (essentially "inducing" a very short ventilation of the prop to help the engine spool up).


    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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  6. Member
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    #6
    Go back to stock. The tuner will not do anything but give you setup problems.

    JM 0.02 cents.







  7. Member
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    Feb 2006
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    #7
    The stock tuner is hard to beat. By shortening the length you loose low end torque. A lightened flywheel will help some but won't bring it back to where it was. If you try that do not go any lighter than 11 lbs. If you go lighter the motor may want to die when changing gears from forward to reverse. That is a real pain while docking the boat.

  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #8
    Definitely agree that the stock tuner is probably your best bet. There was a considerable amount of work done on that particular tuner to squeeze as much performance as possible.


    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).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

  9. Member crank68's Avatar
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    #9
    I would defiantly change it back....
    BULLET 20 XRD/250 Merc Sport XS
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