1986+ Mercury 6/8/9.9/10/15HP 2-stroke Factory Service Manual, Page 87Get this manual
CHARGING AND STARTING SYSTEM
Cleaning and Inspection
1If brushes are pitted, chipped or worn to less than 4.8mm (316 in, replace brushesIMPORTANT: DO NOT clean the starter drive assembly or armature shaft while starter motor is installed on outboardThe cleaning solution will drain dirt into motor housing2If the motor drive assembly does not fully engage with flywheel, the drive assembly may be binding on the helix threads on the armature shaft due to dirt or wearLocate cause of binding and correct before reassembling3Clean drive components with cleaning solution and inspect parts for wear4Clean commutator with No00 sandpaperRemove any oil from commutatorIf commutator surface is pitted, rough or worn unevenly, resurface on lathe5Resurface commutator on lathe as follows: aUse lathe to turn down the commutator surfaceDO NOT turn down the commutator surface excessivelybClean copper particles from slots between commutator barscSand the commutator lightly with No00 sandpaper to remove burrsThoroughly clean the armature after resurfacing and sanding