I use my sailboat on a small lake that does not permit gas motors. And using a small electric trolling motor connected to a 12 volt battery in the cockpit was both a tripping hazard as well as not all that attractive. Another disadvantage was that one battery would not give me the range that I wanted.
This little video-ible shows a trolling motor plug and receptacle as well as a 2 battery set up for an old Venture 17 sailboat.
The run time has been a nice added benefit of having two batteries wired in parallel. The trolling motor is a 12 volt 55# thrust motor. With the motor set on the highest setting the 1,000 (+/-) pound boat will go almost 4mph for about 3.5 hours. Slower speeds will last all day.
Thanks for watching.