Newboy
I have two 85 amp batteries on my boat, they are switchable i.e. bat 1, bat 2 or all on oh and off. I have never had a problem with my batteries except when I forgot to switch the electrical system off when leaving the boat for a period of time (couple of weeks) that spoilt a days fishng but thats another story. Modern electric toys dont drain much power so a 110 amp battery on a small boat is up to the job and will cope with your boat electrics easily.
BUT
I would never have a boat of mine with one battery for safety reasons. With two batteries you should always have plenty of power to start your engine even if one bat goes dead on you. Most outboards can poke out enough power to keep batteries charged up and trailer boaters have the benefit of being able to charge them up at home. Mine are on a trickle charge now. If you are thinking about it you are obviously concerned so dont think it do it, fit two batteries.
Martin