I think so unless you are getting it for free. Even then it is a bit hard to manage.
You do not need a battery with huge cranking amps. The type of battery you need is one that will recover from a sustained relatively low amperage drain. These are commonly known as "deep cycle" batteries.
If you visit your local "Battery World" shop or similar they should be able to give you good advice for your application. They have gel cell batteries (the acid is in a gel form and will not spill out when the boat is heeled over) that cost a bit more but are probably worth it.
Regardless of what type of battery you use it should be fitted in a proper battery box which is fixed or tied down. They have plastic ones that are relatively cheap.
If you are going to be hand starting your engine (recommended on a boat like yours) and you are not going to be running a 12v fridge the expected drain on your battery is your navigation lights, VHF radio (make sure you get one and a restricted Marine Radio Operator's Licence), depth sounder, GPS unit, cabin lights and your stereo CD/tuner. Tell your battery dealer about this and he will recommend a battery that will be the same size or slightly larger than what is fitted to 6 cyl motor cars like Falcons and Commodores.
By the looks of it the solar panel on your cabin top should keep a battery like the above charged up. It might pay to take it into the shop for them to assess and or test.
Tim, you appear to be a relative "babe in the woods" when it comes to this sailing thing. The boat you have bought is a whizz bang sailer and has a fairly sophisticated rig on it. I would hate to see you take it out and break things on the first couple of times out and thereby kill your obvious enthusiasm.
Sydney Harbour is a fantastic place to learn a yacht, cruising or racing, with beautiful anchorages all over the place. Seek the broker's advice on which would be a suitable sailing club for you to join and offer the boat within the club for regular racing with one of their experienced people as skipper and you as novice crew. If the skipper happens to be 5 years younger than you, get over it.
If you do this at every available opportunity (every weekend sounds good), for one year I think both you and the boat will be well prepared for ventureing beyond Sydney Harbour.
There is a down side to this. By that stage you will probably have to be fighting the women off.
Getting advices via this forum is well and good but there is no substitute for practical experience. Get yourself a local sailing mentor. You might like to try via this forum by posting a thread "Sailing Mentor Wanted, Sydney Harbour. I have Boat." It's worth a try, just keep your wits about you.
Best of Luck, Happy Sailing, Cheers Cisco
Tsmithy call immediately when you have to start fighting the women off
sorry Tsmithy
