Im pretty sure there is already a thread on this but whatever.
You do not need a tutor to do well in 4 unit, but of course it depends on your ability.
I have never had tutoring in maths, and never learnt anything before we were taught it class (so I didnt self-teach myself 4unit in year 11 like some people). Obviously I havent done the HSC yet, so I cant compare my results with the rest of the state, although I topped both 3 and 4 unit in my school with averages >90% in both.
Its just about working hard, and working smart. Dont let work get on top of you. If there is something you dont understand, try and work it out yourself. Honestly, working things out for yourself is probably more beneficial than having a tutor explain it to you anyway, because you go through the process of doing it (it is almost like training your brain to work out problems, which is expecially important for harder 3unit question, because often youll get a question like nothing youve seen before and you have to work out what to do with it). And if you still cant do it, ask your teacher, i'm sure theyll help.
Also, keep practicing the whole year round. Once you finish learning a topic in class, go through a past HSC book and do all the questions that relate to that topic, so you become confident in them way before the HSC