If all you are doing is starting the motor, a cranking battery will be fine. If you are also powering livewell,baitwell,electronics, stereo, running lights for extended periods of time, a deep cycle battery will serve you better. A deep cycle will start your motor for years and run everything attached to it, a cranking battery will start your motor for years but will not run everything else as long as a deep cycle will. In a weekend of fishing, how long are you actually turning the key and cranking the motor, if the motor starts like it should, most likely less than minute or two at most.