Patience, who won silver at London 2012 with Stuart Bithell, will compete at the Games in August with new partner Chris Grube.
"It's still a special day but mixed feelings I suppose because I am combining two campaigns to try and still achieve the same goal," said the Scot in a Team GB statement.
"It was wonderful to do this today with Chris and it was wonderful to do that day with Elliot as well...I hope I can draw on the London experience, and with Chris being a first time Olympian, between us it will keep things grounded."
Patience and Willis, a two times world champion, had qualified last year but the pair were withdrawn after the latter's illness was diagnosed in December.
Britain is traditionally strong in Olympic sailing and has won 55 medals, including 26 golds, since the sport made its debut at the 1900 Paris Games. The 470 is a 4.70 metre (15.4ft) dinghy.
"My selection has obviously come out of Elliot’s misfortune but we are going to do our best and hopefully get a medal and do Elliot and ourselves proud," said Grube.
(Reporting by Alan Baldwin, editing by Pritha Sarkar)
