Originally I had a pair of O'Reilly's 500CA (1ST-MATEJ) marine batteries. These were only a couple of months old, but I've been using (abusing) the heavily during
my motor tinkering. For most of the time I had these connected to a charger because I was constantly turning the motor without firing.
suspect of their condition as they were taking longer and longer to recover after starting
attempts. Also I saw online that there were better batteries that O'Reilly's sells that are only $20
I took them back to O'Reilly's to see what they could do so I
could upgrade and they said one had a bad cell and the other was about
shot. They credited me towards a pair of 1000CA (24MSJ) marine
batteries. Extra juice always helps when starting the boat.