1998 Johnson Evinrude "EC" 90, 115 SPL Service Manual, P/N 520209, Page 97Get 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 cover on the spark plug, apply light coating of CWIC Electrical Grease to the ribbed portion of the spark plug ceramic and to the opening of the spark plug coverThis will help prevent corrosion of the spring terminal on the spark plug which can cause high tension arcing