Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 50Get this manual
Starter Cleaning, Inspection and Testing CLEANING AND INSPECTION
1Clean all starter motor parts2Check pinion teeth fo chips, cracks or excessive wear
9Repair barsthat are not too badly burned, by reso ldering the leads in bars (using rosin flu solder) and turning down the commutator in lathe to remove burned material, then undercut the mica10Clean out the copper or brush dust rom slots between the commutator bars11 Check the armature for ground (See the foll owin procedu re "Testing ")