I'd only consider a mooring if I was in the area to check the boat regularly and pull it out if the weather looked like turning, even at that it would only be for a few days. 

Trailer on the hardstand at the marina might be an option, I hear a tinny anchored at Busso was submerged and washed ashore just recently.

3 months is a fair while not to flush an engine - things like thermostats get salted up pretty quick
That aside - over the years I have had my CC in the water down there on a mooring for 2 weeks over the xmas break and one thing you will be surprised at is how much growth they get on them - if you were keeping it in for 3 months you would need to be cleaning the hull

Hi guys, thanks for all your comments, i will keep my boat on the trailer

There are a number of boats that live in the water at South Perth Yacht club that have outboards. Even with the motor tilted up, the small amount of the leg that is in the water gets an offensive amount of growth on it.

 As far as leaving it without flushing....I think it's fine as long as it is being used regularly.  (daily or every 2nd day) have been taking mine up north for weeks at a time as well as leaving it tied to a jetty in Mandurah for week or so at a time and never had a problem.  regular use is the key to keeping the corrosion at bay......at least that's what I tell the missus.

Thanks for the feed back guys I appreciate it