that little tank is also for fuel, we call them Hopper tank.

There are a good number of people that uses the Hopper tank system, the carb gets its fuel from the smaller tank and the small tank (the hopper) gets its fuel from the bigger tank.

This means that your always running with a full tank, you always have a constant supply of fuel regardless of how rough the water is or how much left and right turns your doing, it also eliminates that lean run you get when the tank is getting low (unless you empty the hopper as well).

Dan.