Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 58Get this manual
Starter Cleaning, Inspection and Testing CLEANING AND INSPECTION
123456Clean all starter motor partsCheck pinion teeth for chips, cracks or excessive wearReplace the drive clutch spring andor collar if tension is not adequate or if wear is excessiveInspect brush holder for damage or for failure to hold brushes against commutatorReplace brushes that are pitted or worn to less than 14 in(6.4mm) in lengthInspect the armature conductor (commutator bar junction) for tight connectionA loose connection (excessive heat from prolonged cranking melts solder joints) results in burned commutator bar
TESTING
Armature Test for Shorts
Check armature for short circuits by placing on growler and holding hack saw blade over armature core while armature is rotated If saw blade vibrates, armature is shorted Recheck after cleaning between commutator barsIf saw blade still vibrates, replace armature