End of last year my starter was starting to act up. Took it apart today, and the bottom of it where the brushes are located is not pretty, oily dried out gunk. Bought this boat used several years ago, so not sure what happened to cause this? Would using cleaning solvent on the brushes and armature hurt anything? Brushes look ok, just filthy, need cleaning, and then need to relube the bushings.

Not fuel injected related, but alot of knowledge here to ask.
Any thoughts and insight are appreciated.

Thanks