The fuse is on a ground wire that is put in the motor to help with RFI.
For RFI purposes, it does the same as a ground wire to the motor skeg as a measure to deal with it.
Typically a fuse is not required on a ground wire, but stuff happens.
A motor hooked to some chargers when charging the batteries can blow that fuse. When you are charging your batteries, unplug the motor from the bow receptacle.