Honda BF35A-BF45A Outboard Motors Shop Manual., Page 233Get this manual
CARBURETOR ACCELERATIONDECELERATION SYSTEM
At acceleration When the throttle is opened quickly for sharp acceleration of the outboard motor from constant speed, the diaphragm moves to the full stroke position at the set angle of the throttle cam, and the carburetor main well is pressured instantaneously and the fuel in the well is discharged through the main nozzle by the air pushed by the diaphragmWhen the throttle is opened slowly, the pressured air is bled through the air bleed and air jet not to discharge the fuel excessively