Better late than never on my part….
So the Delco Remy starter’s Mercury part # is 50-31976. The first model Merc 1000, and 850s use it, too.
A brush kit for it would be Mercury # 31197 and a brush spring is 24-31170.
The original Delco starter superseded to #58788A3. My guess is that it is probably Bosch, the kind with the flat commutator and permanent magnets.
Long live American manufacturing!
