1983 Yamaha 30EN Outboards Service Manual, Page 127Get this manual
3 Check continuity between the armature coil and groundIf there is continuity, the armature coil is grounded and therefore should be replaced
5 Through-bolt
I nspection and repair Armature 1Check the surfaces of the commutatorUsing sandpaper (#500 or #600), smooth out any rough surfaceIf roughened excessively, turn the commutator in latheIf run-out is O.2mm (0.008 in) or more, repeat the same step2Measure the commutator mica undercutIf the depth is 0.5 mm (0.02 in) or less, cut it to the specification0.8mm (0.02 0.03 Undercut: 0.5 in)