2000-2005 Yamaha F40B Outboard Service Manual, Page 88Get this manual
.1CONTROL SYSTEM
ADJUSTING THE PILOT SCREW
Do not adjust the carburetor when it is operating properlyExcess adjustment may cause the engine poor performance1Check: Engine idling speed Unstable Adjust2Adjust: Pilot screws NOTE: _ Depending on the model, each pilot screw is covered with blind plugs
Adjustment steps (1) Turn in all of the pilot screws CD until they are lightly seated(2) Turn out the pilot screws the specified number of turnsPilot screw setting 2::1::12 turns out