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  1. #1
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    300xs mad efi mid power loss

    Hi all, please feel free too weigh in.

    Just changed over to a Mad EFI 15 mid on my 300xs
    Issue I have run into is that I have lost bottom end and top end power. The very same prop that would pull a single skier at 90-91mph and 2 skiers 84.4mph now struggles to pull 1 skier out without a massive whip and only getting 83mph.
    I have changed the jacking plate so the offset to the transom is same as when the 20" mid was fitted.

    Has anyone had similar issues?.
    Is there something else that needs to be done to exhaust?.
    Does anyone do ecu reflash to accommodate mid section disruption to factory power curves.

  2. #2
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    Mad EFI Mid

    Quote Originally Posted by MickFaheySM View Post
    Hi all, please feel free too weigh in.

    Just changed over to a Mad EFI 15 mid on my 300xs
    Issue I have run into is that I have lost bottom end and top end power. The very same prop that would pull a single skier at 90-91mph and 2 skiers 84.4mph now struggles to pull 1 skier out without a massive whip and only getting 83mph.
    I have changed the jacking plate so the offset to the transom is same as when the 20" mid was fitted.

    Has anyone had similar issues?.
    Is there something else that needs to be done to exhaust?.
    Does anyone do ecu reflash to accommodate mid section disruption to factory power curves.
    The exhaust breathing on a MAD EFI mid is completely different than a stock mid. I would guess that there is no exhaust back pressure pulses going on with the MAD EFI mid and it's affected top and bottom end performance. Not sure that ecu reflash would help? What exhaust tuner are you using? OEM?

  3. #3
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    Quote Originally Posted by WaterZebra View Post
    The exhaust breathing on a MAD EFI mid is completely different than a stock mid. I would guess that there is no exhaust back pressure pulses going on with the MAD EFI mid and it's affected top and bottom end performance. Not sure that ecu reflash would help? What exhaust tuner are you using? OEM?

    I purchased a MadEFI tuner when I purchased the can off Todd.
    Not sure if there is anything else I should do, block off exhaust from can or block of exhaust into gearbox

  4. #4
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    The mid change shouldn't have slowed the boat down. There is either a setup issue or assembly issue. Since we took 5 inches off and the jackplate was changed was it lowered so the geaecase can run in the same prop to pad height? Are your rpms the same as before when running wide open? Feel free to call me (239)293-4731 or email info@madefi.com

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  6. #5
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    My guess is if the exhaust flows with less restriction it has made it lean?

  7. #6
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    20 to 15 Is a BIG Change

    Quote Originally Posted by MickFaheySM View Post
    Hi all, please feel free too weigh in.

    Just changed over to a Mad EFI 15 mid on my 300xs
    Issue I have run into is that I have lost bottom end and top end power. The very same prop that would pull a single skier at 90-91mph and 2 skiers 84.4mph now struggles to pull 1 skier out without a massive whip and only getting 83mph.
    I have changed the jacking plate so the offset to the transom is same as when the 20" mid was fitted.

    Has anyone had similar issues?.
    Is there something else that needs to be done to exhaust?.
    Does anyone do ecu reflash to accommodate mid section disruption to factory power curves.
    Shrinking shaft length from 20" to 15" is a BIG change let alone expecting to pull skiers? I am not sure this was a good idea.

  8. #7
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    Call Todd you have missed something I have done several and never saw a power or speed drop. Every Super Stock boat is running the 15 inch can and Mercury hands them stock sealed ECU just before the race , none of the racers would run something that hurt speed or power.
    24 Twister

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