I am a rookie at this, but on many threads, I see guys using AN 8,10, or 12 fuel lines on carb boat engines. I just can't understand how the needle and seat in a holley carb can out flow even a 3/8 inch fuel line, much less a 1/2 inch fuel line.
Can someone please explain to me how you can get enough gph through a tiny little jet in the bowl of a carb to suck it dry when the bowl is being supplied with a 1/2 inch line at 9 psi fuel pressure? I know it happens, I just can't imagine how, please help a confused boater.
I would surely think that if the needle and seat weren't the largest restriction, then the jets surely would be. Nobody is running with even 1/8 inch jets right?

8psi would be the max for needles and seats.
And also, some engines have 2 bowls while others have 4 to keep full.
VERY important to keep a good amount of fuel flowing in this type of application.

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The relationship of pressure to volume is inversely proportional. That is, as
pressure increases the volume will decrease, everything else being equal. A
certain amount of fuel pressure is always required to maintain engine performance
by assuring that fuel is available on demand. Also, other factors
and conditions must be taken into account such as acceleration G-forces and
friction within the fuel system itself. At the same time,however, an adequate
fuel volume is needed to ensure that the proper amount of fuel can always
flow to the engine, especially during peak demand situations. A basic understanding
of this critical pressure/volume relationship is needed when designing
the proper fuel supply system.