Hey Jerry:

I never put a circuit breaker on my PowerDrive. And I never had any problems. However, for all I know, maybe through time not having a circuit breaker caused a bit of "frying" and subsequent loss of power through the years.

If you are going to do it I would put an inline 50 amp circuit breaker complete with power swith into the positive feed.

Did you ever solve the problem of how to mount your motor to your boat?