1992 Johnson Evinrude "EN" 9.9 thru 30 Service Manual, P/N 508142, Page 306Get this manual
Cleaning and Inspection
1Inspect the brushes; replace if one-half worn, damaged, or crackedReplace brush springs, if weak2Clean commutator with 300 grade emery clothIf commutator surface is unevenly worn or pitted, turn on latheRemove any trace of oil or metal dust from commutator'5l1sl 3Check the armature on growler for shorted turnsCheck armature for grounding by using test light or meterInspect armature insulation for indications of overheating or damaged windingsClean off any deposits of carbon or foreign matter which may contribute to later failure of the windings
71 4Check permanent magnetsMagnets should strongly attract