I am a firm believer in having a main starting battery with 1000 MCA running only bilge pump, running lights and vhf accessories. Two group 27/31 deep cycle batteries are used for my 80lb electric trolling motor. I run a separate group 27 deep cycle battery for 2 fish finders and 2 Scotty downriggers. All batteries are Interstate wet series providing an average 5/6 years of use.