i put a new 502 in my boat, it has a carb on it .i see mercruiser uses a 1 inch carb spacer on there 502 mag carb model what does the spacer do thanks mike

It increases plenum volume....sorta like a short tunnel ram manifold. It can also act as an insulator, keeping the carb (and fuel) cooler. 4 hole spacers are usually run on dual plane intakes...and open spacers on single plane intakes.

Try this link...as it should help you understand better sir.

http://forums.hybridz.org/index.php/...s-it-for-real/