1996-2005 Suzuki DF40, DF50 Four Stroke Outboard Service Manual, Page 74Get this manual
3-19 ENGINE CONTROL SYSTEM
AIR INTAKE COMPONENTS
Air, after entering through the silencer, passes through the throttle body and flows into the surge tank where it is then distributed to the cylinder intake manifoldIntake manifold pressure, monitored by the MAP sensor, is an indirect measure of the intake air amountWhen the throttle is fully closed, the main supply of intake manifold air necessary to sustain engine idle passes through the by-pass air passageTo maintain engine idle speed at specification, the ECM controlled IAC valve supplies regulated amount of additional air through the IAC (idle air control) passage
By-pass air screw Intake manifold
Throttle body By-pass air passage
AIR FLOW
Flame arrester