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  1. #1
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    Default whats the diff between marine carb and auto carb?

    i was just wondering if there is much difence in an marine and auto carb . im wanting to get a new one . or if anyone knows a good place to get one at a cheap price the one i have now is a rochester 2bbl # 173 7028188 thanks for the help
    1989 Celebrity 181
    4.3L (175hp) alpha one

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Yes, there is a big difference, and an automotive carb should never be used in a boat.
    The marine carbs are designed to have any excess gas in the fuel bowls and vents, vented into the engine and not outside as in automotive carbs. It's a safety issue to prevent fires and explosions. Same with many of the electrical components, alt, starter, distributor, etc. ALWAYS marine, not automotive.
    Don S.


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  3. #3
    Vice Admiral Scaaty's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Short version......

    Slight gas leak from stuck float........

    Marine Carb...runs a little rough

    Auto Carb...fireball.... and make the front page AND the news. Plus your Insurance won't pay

  4. #4
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    Default Re: whats the diff between marine carb and auto carb?

    I also went through this with a 2 barrel Rochester. The previous owner had an auto carb in it and the boat never ran right. The outside looks similar, but internally it is slightly different and never ran right over about 3/4 throttle. Don't do it even though it's much cheaper. You will have issues.

  5. #5
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    Default Re: whats the diff between marine carb and auto carb?

    how do you know if you have one already on it ? is there a way to tell
    1989 Celebrity 181
    4.3L (175hp) alpha one

  6. #6
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    That carb is for a 1968 Kiekhaefer (aka Mercruiser) 6 cyl 250. It is a marine carb.

    Google is a wonderful thing

    http://www.thecarburetorshop.com/MkitDthruK.htm

    Just out of curiosity, what engine do you have and what year?


    Don S.


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  7. #7
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    Default Re: whats the diff between marine carb and auto carb?

    Kiekhaefer 1968 6 250 Rochester 7028188 2GC 2821

    Looks like you already have a marine carb.

  8. #8
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    Default Re: whats the diff between marine carb and auto carb?

    thanks for the help ts a 160hp mercrusier 4.1 250 the motor is a 67
    1989 Celebrity 181
    4.3L (175hp) alpha one

  9. #9
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    Default Re: whats the diff between marine carb and auto carb?

    pic
    Attached Images Attached Images
    1989 Celebrity 181
    4.3L (175hp) alpha one

  10. #10
    Supreme Mariner Boomyal's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Other differences not mentioned. Marine carbs have better sealing at the throttle shaft to prevent leakage out into the engine compartment. Also, at least some like Holley, have a more corrosion resistant finish on the outside.

  11. #11
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Marine carbs have better sealing at the throttle shaft to prevent leakage out into the engine compartment.
    Are you sure about that? I don't recall any differences there. It's on the vacuum side anyway and would suck air, not leak fuel.
    Don S.


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  12. #12
    Supreme Mariner Boomyal's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Quote Originally Posted by Don
    Marine carbs have better sealing at the throttle shaft to prevent leakage out into the engine compartment.
    Are you sure about that? I don't recall any differences there. It's on the vacuum side anyway and would suck air, not leak fuel.
    Don, I'm sure that I read that on the Holley site.

  13. #13
    Vice Admiral Scaaty's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Didn't make sense to me either, but my old Q-junk dribbled a drop or two when shut off out the shaft. Long ago, can't remember much about the ifs, and's or butts

  14. #14
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    Default Re: whats the diff between marine carb and auto carb?

    Sealed Accelerator pump shaft, spring loaded check balls, and special marine bowel venting to mention a few others......
    Just owning a boat does not make you a boater!!

    " Life is so much better on a boat " SS MAYFLOAT

    "All that is necessary for evil to win the world is for good men to do......................nothing" Edmund Burke

    "A simple way to take measure of a country is to look at how many want in, and how many want to get out." Prime Minister Tony Blair

    Page 2,
    Class of '05




  15. #15
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    Default Re: whats the diff between marine carb and auto carb?

    I was wondering if the marine holley has a different float setting, especially for the rear bowl. When mounted to my engine the carb has a drastic tilt towards the rear of the boat. My father-in-law (who is a hot rod freak) made the observation and said that a normal carb would have float problem tilted like that all the time.

  16. #16
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: whats the diff between marine carb and auto carb?

    Sure they have different settings than automotive.
    The engines usually sit pretty leverl in an IO engine, maybe a little angle, but not enough to worry about. That is in the disign of the boat.
    If you have a very steep angle, such as in some inboard installations, there are special intake manifolds and angled spacers that go under the carb to keep it fairly level.
    Don S.


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  17. #17
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    Default Re: whats the diff between marine carb and auto carb?

    huh, my inboard doesn't have one but that doesn't mean it shouldn't

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