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Thread: Carb to Throttle Body

  1. #1
    Member OKElkHunter's Avatar
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    Jan 2007

    Default Carb to Throttle Body

    I am thinking about switching from a carb to a throttle body injection. Has anyone done this? I have a 5L Mercrusier and would like to squeeze a little more efficiency out of her without making major modifications. Is this feasible; if so, how much work would it be? I know I'd have to switch to an electric fuel pump, and would have to get the throttle body, but would the intake have to be changed? I believe the 5L Mercruiser is a Chevy 5L (305CID); is this correct? I am pretty skilled at working on auto engines and switching intakes and fuel pumps is no big deal. I've rebuilt numerous small and big block auto engines over the years and have even done some performance work on Pontiac Firebird with a 350.
    “Don't expect to build up the weak by pulling down the strong." ~Calvin Coolidge~

  2. #2
    Member avidflyer's Avatar
    Join Date
    May 2007


    I have done it on a couple boats. one was the holley TB and it used the same intake. Easy swap that took a couple hours start to finish. The other was using Multi port from affordable marine. It took a bit longer to swap as you have to swap manifolds and sensors, but still an afternoon swap. After going to the multi port, fuel burn was less than half of what I burned with a carb. TB was about a 40% reduction in fuel burn. This was on a 28' BL trophy with a 350.

  3. #3
    Member Akgramps's Avatar
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    Apr 2008
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    Avidflyer, Those are huge savings, it would not take too long to pay for EFI at that rate. We have a rebuilt 1998 5.7 Mercruiser we plan to use on a 24' Glasply......still a ways out. Looking at the prices on Affordables website didnt scare me too bad. Wondering, where does the 02 sensor go?

    Can you still use a FloScan?
    “Nothing worth doing is easy”


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