[1] Willoughby was first selected to represent South Australia in the 1975 senior men's eight which contested the King's Cup at the Interstate Regatta.

[5] He was selected in 1981 to a coxed four with Graham Jones, Jim Battersby and John Bentley who raced at the 1981 World Rowing Championships in Munich to a sixth placing.

[5] In 1983, Willoughby secured the six seat of the Australian eight selected within a limited squad sent to the 1983 World Rowing Championships in Duisburg Germany.

In the final at the World Championships the Australian crew drew a bad lane and lost the benefit of the tail breeze however they raced a strong second 1000m and finished in third place for a bronze medal.

[6] The Australian eight selected for the 1984 Los Angeles Olympics was built around the national champion Mosman Rowing Club coxed four of Jim Battersby, Craig Muller and Steve Evans.