I spent a day at sea taking my Raymarine motor apart after the solder holding the brushes melted and the brushes fell off. The motor was sealed but 'hey!' we're at sea on a 5 day passage with no auto pilot. I managed to get it working and during the rest of the trip used the auto pilot sparingly so it didn't overhead ( a problem with that motor ).

I found a replacement motor 'forget the name' that is used on all the Nordhaven's running a Raymarine auto pilot. It worked flawlessly and had replaceable brushes which I purchased and taped to the motor for backup future needs.

A motor that has brushes you can't replace is a real bummer and not a motor to have on a boat unless it's brushless.