Question: when did australia 2 win the america's cup?
Answer: 1983

The 1983 America's Cup was the occasion of the first winning challenge to the New York Yacht Club, which had successfully defended the cup over a period of 132 years.  An Australian syndicate representing the Royal Perth Yacht Club fielded the Australia II, skippered by John Bertrand, against defender Liberty, skippered by Dennis Conner. Australia II won the match races to win the America's Cup, ending the longest winning streak in sporting history and ending U.S. domination of the racing series.