In 1938, at 18 years old, Cusack became the Secretary of the newly formed Maryborough Amateur Swimming Club. He, along with Des Ramsay, became a Coach at the club at the end of the
Second World War.
David Theile was initially coached by Ramsay, but soon switched to Cusack, even though Cusack was thought to be a difficult coach by many swimmers, as he would require long, tiring sessions in the pool. In 1958, Cusack left Maryborough. In 1962, Cusack was appointed as a coach on the Australian
1962 Commonwealth Games team in
Perth. In the mid-60s, Cusack took over the lease of the Centenary Pool in Brisbane. It was from here that he would take on the coaching of his nephew
Robert Cusack into the Australian Olympic Team. ==Coaching highlights==