Long story short, I think my original Interstate group 27 cranking battery is going dead. The voltmeter says it is holding a charge but it didn't want to start the boat yesterday morning after charging all night. Anyway, I'd like to get an AGM to replace, but I'd like to stay with 27 if possible. I'm not even sure anyone makes 27 AGM. I have a Ranger RT188 w/ a 115 Merc 4s, there isn't a lot of room in the bilge, for a 31. Though, it can be done. Also, can I charge 1 AGM and 2 wet batteries with a Dual Pro, recreation series 3x6 charger? My last boat I had a MK 345 PC charger and ran 1 31AGM and 2 wet cells, but the PC charger allows that.