Darter don't be deterred because u found one bad egg mate there are tons of great boats out there, Have u tried looking on Gumtree.com.au?
if your going to piece a rig together i would suggest buying a older model Honda, Yamaha, Mercury 4 stroke 40hp u should be able to pick one up on Gumtree for around $2000 $2350 if u haggle it leaves u a bit of coin to buy a hull and trailer but usually if u set out on a 4k budget in summer a lot of people ask to much for there boats because it is the silly season and everyone wants to go boating and fishing
in winter the last thought on someone's mine is getting your shoes off in 14c weather with water just as cold to launch the boat so its harder for people to sell a boat in winter and a lot easier to find a cheaper and better rig as a buyer
a lot of people try sell their boats in winter too because they arn't using them for a good portion of the year people see it as invested money just depreciating when a boat sits throughout the colder months