Re: why do big outboard motors have more than one carb
The "real" reason is efficiency/horsepower. The ideal two-stroke engine would have the fuel/air charge go straight into and through the crankcase to the cylinders.
As an outrageous example, supose we had a 6 cylinder in-line engine with only one carburetor in the center, manifolded to all 6 cylinders. The charge would have to be directed up and down to the top and bottom cylinders, making a Z-turn as it goes. Same thing for number 2 and 5 cylinders, but a shorter path. Also, same thing for number 3 and 4, but a shorter path yet. Are you noticing a distinct imbalance there? And notice all the Z-turns. Every time it makes a turn, efficiency is lost. Now if we were to put 6 carburetors on that engine, all 6 would have equal paths, and no Z-turns. Much higher horsepower because of less waste of efficiency. And less pollution too, because every time the charge splats up against a wall such as at the ends of the Z, fuel separates from the air and runs down hill. Down hill usually means into the lake.