07-22-2016 05:08 - edited 07-22-2016 05:09
For best results use a marine battery to which you can add distilled water if needed. Either a marine starting battery or a marine deep cycle battery is OK as long as it has a minimum of 500 cold cranking amps(CCA). In cold weather 675 CCA is required. This does not take into account the electrical requirements of the accessories on the boat. Get the highest capacity battery that you can afford and fit. Do not confuse MCA ratings with CCA ratings.
AGM batteries are very expensive and require a specialized charging voltage and procedure. Because outboard motor charging sytems are not designed for them, AGM battery life is shorter in marine environment.