2002/2003 Johnson SN/ST 2 Stroke 3.5, 6 8 HP Outboards Service Manual, PN 5005466, Page 130Get this manual
FUEL SYSTEM CARBURETOR68
Carburetor Adjustment
IMPORTANT: The slow-speed mixture in this
carburetor is controlled by an adjustable needle
Start the engine and run it in gear at idle speed for three minutesAllow it to reach normal operating temperatureIf the adjustment is too lean, the engine will sneeze and backfireDo the following procedure: Note the reference mark and turn the needle 18 revolution counterclockwiseWait 15 seconds after each adjustment and repeat this procedure until you reach the highest consistent RPM If the adjustment is too rich, the engine will be rough and unsteadyDo the following procedure: Note the reference mark and turn the needle 18 revolution clockwiseWait 15 seconds after each adjustment and repeat this procedure until you reach the highest consistent RPMTo test the adjustment, run engine near full throttle for three minutesReturn the engine to idle, in gearThe engine should maintain smooth idle RPMIf the test results vary, go to STEP and repeat the adjustment again If the engine does not respond properly to these adjustments, check the following: Engine temperature and linkage Sufficient exhaust back pressure