Honda Outboards BF40A/BF50A Service Manual, Page 412Get this manual
BF40A-BF50A -Armature 1) Check the armature for wear and damageReplace if necessary
2) Visually inspect the commutator surface for dust, rust and other damageIf necessary, wipe it with clean lint-free cloth or dress with fine emery cloth3) Measure the mica depthIf the grooves are clogged,
[1MICA DEPTH
clean the grooves and measure the depth againIf the measurement is less than the service limit, replace the armatureService limit 1.3 mm (0.05 in)