I bought the largest one they carry I believe it's a 31 series for my 250 HPDI running aerator most of the day as well as a Bird 998 and 1199 all day and also a power pole. Been using it a year now without any issues at all including night fishing while running navigation lights.
Always get 31. But check with sears. I was told odyssey makes sears marine batteries. They are supper heavy but they run forever. I have three graphs, two live wells, two talons working a lot and she will still crank that 250 SHO with no problem.
The biggest problem with marine batteries is that some people do not put them on charge as soon as they get home, the faster you get them on the charger the longer the life you will get out of them. If your motor charges your battery while it is running and you keep proper maintenance your battery should last the minimum of the warranty that is offered or longer. My starting battery is just now giving me problems but it is 3 years old so I have got more use out of it than the warranty offers. Most lead batteries are designed not to last more than 2 years so anything past that is a bonus. Good luck