2003 Johnson ST 55 HP WRL 2 Stroke Commercial Service Manual, PN 5005483, Page 54Get this manual
MAINTENANCE
SPARK PLUGS
Air Silencer
The air silencer minimizes audible noise related to air flow into the engineAdditionally, it collects any fluid residue that migrates from the leaf plate or the throttle body area
SPARK PLUGS
Remove and inspect the spark plugs for the following conditions: Worn electrodes Cracked insulator Dirty spark plugs Replace all defective spark plugsBefore installing the spark plug lead cover on the spark plug, apply light coating of Electrical Grease to the ribbed portion of the spark plug ceramic and to the opening of the spark plug coverSee table below for recommended spark plug data and gap settingModels Recommended
Air silencer