2004 SR Johnson 2 Stroke 9.9, 15, 25, 30 HP Outboards Service Manual, Page 163Get this manual
FUEL SYSTEM CARBURETOR MIXTURE ADJUSTMENT
2530 MODELS
Make reference mark on the carburetor body before you disturb the needle adjustment
Start the engine and run it in gear, at slow speed (700 to 800 RPM)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 richthe 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 RPMTest the adjustmentRun outboard near full throttle for three minutesReturn the outboard to idle, in gearThe outboard should maintain smooth idle RPM If the test results vary, repeat the adjustmentIf the outboard does not respond properly to these adjustments, check the followingEngine temperature Linkage adjustments External recirculation system Sufficient exhaust back pressure