During the 1987 Fijian coups d'état, Sinclair was in charge of the evacuation of all Australian citizens from Fiji. In 1989, he was appointed as Deputy Chief of the Naval Staff. He served only briefly and in that same year he retired from the Navy to take up cattle breeding at "Kirkbreck" a property near Tea Gardens, New South Wales. In 1990, the Premier of New South Wales, Nick Greiner, asked Sinclair to coordinate the Flood Relief Operations during the Nyngan and Bogan Shire floods.