Evening slick,
From Qld Tpt Handbook, page7:
All boats fitted with a motor or aux engine of over 4HP require registration.
Page 41:
A licence is required when operating a boat powered by a motor over 4.5KW (6HP) that is capable of speeds over 10 knots & has a planing hull.
The book is free from Qld Tpt offices. May save you some $$$$ if you are not complying.