Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 202Get this manual
Testing 1Check and clean armature as follows: aIf commutator is worn, it can be turned down on an armature conditioner tool or on lathebIf not worn badly, clean commutator with "00" sandpapercCheck armature on growler(Follow growler manufacturer test instructions Any indication of shorts or open windings requires replacement of armature2Inspect commutator end plate as follows: aCheck thermal overload switch for full continuityConnnect leads of Ohmmeter (Rx1 scale) between brush pigtail and opposite end of thermal overload switch, as shown If meter indicates no continuity or high resistance, replace end plate