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Patience and Willis, a two times world champion, had qualified last year but the pair were withdrawn after the latter's illness was diagnosed in December.
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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)
