Im only 17 so not wanting to spend over $5000
i want the boat for fishing, diving and getting to surf locations such as rottnest island maybe towning in??
i dont want a metal dingy type boat or anything to loud
what questions should l ask when purchasing a second hand boat?
what do l have to check for when buying a boat condition?
what boats are most fuel efficent?
i am totally new to boats so any advice would be helpful
thnx everyone
what brands are the best?

Try posting ur questions one at a time. 5000 will get u a good boat. You need something unsinkable. l would say a del quay dory would come in ur price range. The ultimate would be a Boston Whaler but l do not know if u can find one in that price range with a reasonably new motor. You can saw them both in half & get home. The motor is where u put ur money. For good gas milage u will want to try to get a 4 cycle, but they r usually pretty new & expensive. Do not let that stop u from being a boat owner. The boat u r buying will sell for the same price next season so buy a boat & upgrade next year if u want something better.

the crucial parts are: transom, and engine.

if the transom has any soft spots, it is a major headache.

at a minimum, check the compression, if the worst cylinder is not within 5% of the best, walk away.

no boat is fuel efficient, but four-stroke engines are more so than 2-stroke and a shallower hull will be more so than deeper (all else being equal).