whats the diff between marine carb and auto carb?

waterdawg69

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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
 

Don S

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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.
 

Scaaty

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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
 

ntheyer

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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.
 

waterdawg69

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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
 

Don S

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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?
 

searay3

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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.
 

waterdawg69

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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
 

waterdawg69

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Re: whats the diff between marine carb and auto carb?

pic
 

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Boomyal

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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.
 

Don S

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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.
 

Boomyal

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Re: whats the diff between marine carb and auto carb?

Don said:
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.
 

Scaaty

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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
 

Limited-Time

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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......
 

JasonR

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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.
 

Don S

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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.
 

JasonR

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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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