Tyrone
Are you saying that you found him on the English census of 1891?
Lists of passengers to Victoria, Australia can be found on the PROV site, and looking at Assisted Passengers there are 37 John Williams who might be yours - their ages are given, also the years of sailing, so you can do a calculation to see if any of them fits.
http://www.prov.vic.gov.au/indexes/index_search_results.aspThere are also Unassisted Passenger lists, with 13 John Williams
You could try other state records, too. If you find someone who fits the age, why not put a query on the Australia page here and see if someone can follow that person up?
Good luck with your search.
Gillg