Agree your battery needs will depend on the boat. I ran a 16' with a 35 hp electric start and 36 lb trolling motor on one battery for years with no problem. I had a 27 series Everstart and it lasted almost 7 years...just replaced it and also sold the boat. The 35 was electric or pull start and I usually started it the first time of the day with the starter and after that I used the pull start and it was usually just 1 pull. I managed it with a old Craftsman charger. Now with my new bigger boat I run 3 batteries and a onboard charger.