outboard carb question

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pine island fred

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Dec 20, 2002
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Been rebuilding some carbs today for my YAMAHA and a thought came up that I have never really bothered to question. I have never worked on outboard carbs that have an accelerator pump. No piston or spring loaded diaphragm, nothing. Can someone tell me why?
I have some thoughts but they are just guesses. One would be that each cyl. has a carb and the mixture does not have time to lean out with the sudden increase of air flow. My other thought is that the 2 stroke mixture is rich enough to compensate for the sudden increase in air flow and the carb is close enough to cylinder to quickly compensate. Anyone have any real reason? thanks FRED
 
JB

JB

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Re: outboard carb question

Two strokes do not usually need bursts of fuel to accompany opening the throttle, Fred. A correctly used choke or primer is adequate for starting.
 
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Frank Acampora

Frank Acampora

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Re: outboard carb question

My Suzuki four cycle has an accelerator pump on each of the three carbs. The older 4 cylinder 100 HP Mercury 2 cycle engines have a single accelerator pump. So, there are some out there.
 
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Chris1956

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Re: outboard carb question

Fred, On a lot of the OB carbs, the idle mixture is set a bit rich to substitute for an accelerator pump. As Frank said, I know some Merc models have them.
 
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