alot of people use two batteries a deep cycle for accessories and have a cranking battery for........cranking.
Depending on the size of your boat and the accessories two would be best but if you only go with one make sure you have a booster pack close at hand just incase
Thankyou for your reply, Don't really have any acc. to run just the radio when at the sand bar. I think I will go with the cranking battery with the jump pac for a back-up
Thanks on the dual purpose suggestion can you charge these kind of battery's with a regular 10 amp charger or does it need a trickle charge or does the motor charge both?