Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 91Get this manual
TESTING Armature Test for Shorts
Checking Positive Brushes and Terminal
Check armature for short circuits by placing on growler and holding hack saw blade over armature core while armature is rotatedIf saw blade vibrates, armature is shortedRecheck after cleaning between commutator barsIf saw blade still vibrates, replace armature
Set ohmmeter to (R scale)Connect meter leads between POSITIVE brushesMeter must indicate full continuity or zero resistanceIf resistance is indicated, inspect lead to brush and lead to POSITIVE terminal solder connectionIf connection cannot be repaired, brushes must be replaced