yes higher is fine and IMO would recommend... In my 1900SR I have a group 27 marine starting battery and a group 31 AGM deep cycle... I have a ACR add a battery kit from blue seas systems (https://www.bluesea.com/products/765...ery_Kit_-_120A
) The reason for this is here in San Diego I use my boat for offshore fishing as well as watersports (I have had my boat over 40 miles offshore) and when fishing the battery loads are much larger... I run a bait pump (3.5 amps), VHF (1.5 amps), GPS/Fish finder (2.5 amps), under water lights (6 amps) and various other things that when I drift for up to 6 hours would put a strain on a regular battery and not be safe without a 2nd battery system... I have all power circuits other than starting of engine on the "house" battery... that being said I have both battery's in the port rear corner (120+ pounds worth) and have no issued with the boat being balanced.