1995 Johnson/Evinrude Outboards 9.9, 15 four-stroke Service Manual, Page 75Get this manual
Spark Plug Information The spark plugs should be removed and examinedA spark plug should be replaced if the electrodes are badly worn, if it has cracked insulator, or is badly fouledBefore installing the spark plug lead cover on the spark plug, apply light coating of CIVIC Triple-Guard grease to the ribbed portion of the spark plug ceramic and to the opening of the spark plug coverThis will help prevent corrosion between the spring terminal and the spark plug which can cause high tension arcing