I have run the 31M Optima’s in the past. 2 of the 4 that I ran in my boat failed after 2 months of use. The starting battery never had enough energy to keep my electronics and accessories running all day and needed to add an extra for that. The power for the TM started to fall off after 4 hrs of use. When I returned them, the store mgr reported a one in three failure rate. Did a little research on finding a premium battery for my Skeeter and went with the Odyssey PC 2150 31M http://www.odysseybattery.com. and have had more than enough power to get me thru multiple days on the water. Check out the specs,warranty and cycle life on the website.If their good enough for the U.S. military to start their equipment, their good enough to keep me on the water for my guide trips and tournament events. BatteriePlus & Skeeter Boat Center retail them.No more battery issues here, “Got my Odyssey’s”