Career
McMahon played two matches for Auckland in the Plunket Shield in 1936-1937 and 1937-1938 as a leg-spinner without distinguishing himself, although he dismissed the Test batsmen Curly Page and Ian Cromb in his first match. After serving overseas in the New Zealand Third Division in World World War II he played most of his major cricket for Waikato in the Hawke Cup as a middle-order batsman. In 1948-1949 he scored 138 in an innings victory over Bay of Plenty.
He began 1949-1950 by scoring 111 in a drawn match against Hutt Valley, reaching his century in 50 minutes and hitting 12 fours and eight sixes.
In Waikato"s next match, a two-day fixture against the touring Australians, he scored 102 in 157 minutes (12 fours and three sixes) out of a team total of 157. The next best score was 15.
Given that he was 33 and had not played a first-class match for 12 years, his selection for the only match between New Zealand and the Australians three weeks later was unexpected. Even the Australians were surprised, as they had not taken the Waikato match very seriously.
He made 0 and 12, bowled by Jack Iverson each time, and New Zealand narrowly avoided an innings defeat.
He played a few more matches for Waikato in 1950-1951 and 1951-1952. From 1966 to 1990 he organised an annual cricketers" golf day in aid of charity at the North Shore Golf Club in Auckland. He was awarded the for Community Service in the 1995 Birthday Honours.