McCahill was married a number of times but died without issue. In a 1956 interview with
Playboy magazine McCahill stated that he had "more cash than hair". The statement was in response to a question as to how he had been photographed in two separate issues of
Mechanix Illustrated with two different wives. McCahill had homes in Florida and New York, where he would receive cars to test. He traveled all over the United States and Europe to facilitate testing. His stepson with his fourth wife, Brooks Brender, served as McCahill's assistant in his later years. McCahill was a personal friend of band leader
Paul Whiteman, with whom he shared his love of hunting and fishing. Every year, McCahill would make a ten-day boating trip from his home in New York to his home in Florida aboard his thirty-foot Egg Harbor Cruiser the "Rooster" (McCahill was forced to sell the Rooster in 1967 to pay off back taxes to the IRS). McCahill was an avid fisherman, hunter and deep-sea diver. At age 68, McCahill died at the Daytona Community Hospital on May 10, 1975.
Mechanix Illustrated never publicly acknowledged his death, because his name was synonymous with it. He "amounted to the franchise" and management never wanted to admit he was gone. For a while, they ran a column called "McCahill Reports", which was
ghostwritten by Brender. At the time of his death, he was believed to be the only living descendant of the Scottish highwayman
Rob Roy. According to Canadian automotive historian Bill Vance, McCahill had lost a leg that became
gangrenous after a thorn penetrated it during a duck hunt, forcing its amputation. ==Books==