I have a 36 volt trolling motor that is being run with 3 series 30 batteries. I dont have a designated cranking battery. I am wanting to change the trolling batteries to 3 series 27 batteries and add a series 31 for my cranking battery. How would be the best way to arrange this on a 2006 cougar. I also have a power pump that is secured to the seat pedestal. When you put in the oil tank space is limited. Thanks