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  1. #1
    Cadet
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    Default Repower - 357 Mercruiser 4V OR 350 MAG MPI

    Boat is a Sea Ray Sundancer 240 and my old 5.0 EFI (Throttle Body Inj) is shot. Looking to repower with a complete engine package from Mercury. Down to two options:

    1. Reman 357 Bravo 4V carbed, 325 HP (at crank) and 3 year warranty from Mercury

    2. CPO 350 MAG MPI, 300 HP (at prop) - same warranty as above I think.

    I am concerned about the added fuel consumption of the carb motor. I had TBI on my old motor and it still sucked gas. Maybe a tired motor on a heavy boat? Will the carb motor really drink much more gas vs the MPI?? Also, will the driveability / startups be that much better with the MPI?? I have never had carb before on a boat. I only use my boat for about 50 hours a year....Cost difference between the two motors is apprx $1600. Any thoughts appreciated.

    Ed

  2. #2
    Captain
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    Default Re: Repower - 357 Mercruiser 4V OR 350 MAG MPI

    Well, the starting will likely be much quicker with an MPI over the carb, but you won't notice much of a difference other than that. They both have similar HP and fuel efficiency on a properly tuned carb, is similar to that of fuel injection, they just go about it different ways. You'd have to install a high pressure fuel pump with the MPI versus the mechanical version used on the carbs. It's really just a matter of whether the extra $1,600 is worth it for better cold starts (hot starts on both are the same).
    1976 Mark Twain 200VBR w/Mercruiser 233 (Ford 351w) "Heart & Soul"

  3. #3
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    Default Re: Repower - 357 Mercruiser 4V OR 350 MAG MPI

    Quote Originally Posted by haulnazz15 View Post
    Well, the starting will likely be much quicker with an MPI over the carb, but you won't notice much of a difference other than that. They both have similar HP and fuel efficiency on a properly tuned carb, is similar to that of fuel injection, they just go about it different ways. You'd have to install a high pressure fuel pump with the MPI versus the mechanical version used on the carbs. It's really just a matter of whether the extra $1,600 is worth it for better cold starts (hot starts on both are the same).
    Thanks - another consideration I had was the cost of potential future repairs on the MPI engine (fuel pumps, ECU, sensors, etc).

  4. #4
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    Default Re: Repower - 357 Mercruiser 4V OR 350 MAG MPI

    Quote Originally Posted by edsmax View Post
    Thanks - another consideration I had was the cost of potential future repairs on the MPI engine (fuel pumps, ECU, sensors, etc).
    The sensors don't fail often enough to worry about that cost. For the same amount in sensor/pump repairs, you would have to assume the same with mechanical fuel pump and carb rebuild/maintenance. 6 of one/half dozen of another.
    1976 Mark Twain 200VBR w/Mercruiser 233 (Ford 351w) "Heart & Soul"

  5. #5
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    Default Re: Repower - 357 Mercruiser 4V OR 350 MAG MPI

    Conversion is done - went with the 357 MAG 4V. So far very happy and a clean install. Totally different boat with this engine vs the old 5.0.

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