I would use one. You can get a simple 50 amp auto reset from Walmart in there boating section. You would need 4 ring eyes to fit the breaker studs that are big enough to fit the wire you are using. Just cut your battery end of wire about 8 in long, strip both ends, put smattering ring eye one one end and bigger eye to fit battery stud on the other. Then another small eye on end from breaker to motor. Protects motor and boat and you from any chance of wire shorting and starting a fire. Sounds like a lot of stuff to do but really simple and quick once you start. Hardest part is rounding up everything to do the job.

Thank you for Your Service Chief.