2003 Johnson ST 55 HP WRL 2 Stroke Commercial Service Manual, PN 5005483, Page 57Get this manual
MAINTENANCE SYNCHRONIZATION AND LINKAGE
Maximum Spark Advance
Maximum Spark Advance
Adjust the idle speed screw to achieve 800 25 RPM when screw is against its stop
Connect timing light to the No1 spark plug lead and mark the flywheel timing grid at 19 BTDCRun outboard with correct test propeller in test tank at minimum of 5000 RPM in FORWARD gearThe timing pointer at the front of the engine should align with 19 BTDC on the flywheelIf adjustment is required, stop outboard and remove the FORWARD socket from spark leverAdjust the length of the spark control rod by rotating socket clockwise to advance timing or counterclockwise to retard timingTwo revolutions equal approximately one degree of timingReinstall spark control rod and recheck maximum spark advance
1Idle speed screw
DR4551CA
Use timing light to check that timing is ATDC at 800 25 RPM with both throttle plates closed If idle timing is not within range, check CARBURETOR MIXTURE ADJUSTMENT in the FUEL SYSTEM section and repeat idle speed adjustmentTighten the idle speed screw locking nut