Hate to admit it but I've had my $60 Group24 marine battery from W*M for five years and I'm fixin to replace it with a $78 Group27 next week. I'm on a mooring all summer and on the hard from Nov-April, and maintain the battery using a 25W solar panel. I run a few cabin lights, nav lights, VHF and a stereo sound system. No AC, no fridge.
My Honda 8 has an electric start with a 12A alternator. Seems that combo equates to a pretty successful system.
I could go for an AGM or GelCell type battery for 2X the price, but I doubt I'd get twice the performance.