Marlin built his reputation on the short tracks of Tennessee and Alabama, competing regularly against Red Farmer, Bobby Allison, and Donnie Allison. He won four track championships at Nashville Speedway USA, establishing himself as one of the state's most consistent performers at the circuit that would later be renamed Music City Motorplex.
During the 1960s he was a fixture in the Nashville racing scene and became a genuine fan favorite, particularly among young spectators. He drove a fire-engine red 1964 Chevrolet Impala numbered 711, making him something of a hero to a generation of racing fans growing up in the region. His racing rivalry with Charlie Binkley, who drove car No. 125, produced many memorable moments and close finishes that kept crowds entertained. Marlin was consistently accessible to fans after races, signing autographs and posing for photographs in the pits. His brother Jack Marlin was also a popular figure at the same tracks.
Marlin made his first NASCAR Grand National start in 1966, running just one race that season and three in 1967 as a part-time competitor. As the series transitioned from Grand National to Winston Cup branding in 1971, he increased his schedule but never competed in more than 23 races in a single season. Over 165 career Winston Cup starts from 1966 to 1980, Marlin recorded nine top-five and 51 top-ten finishes without ever winning a points-paying race.
He did claim one non-points victory in 1973, winning one of the qualifying Duel races at Daytona International Speedway. A large portion of his Cup Series starts came in a car numbered 14, a number that would take on particular significance for his family after his death.
Marlin died of lung cancer in his hometown of Columbia, Tennessee, on August 14, 2005, at the age of 73. His son Sterling, who was an active Winston Cup competitor at the time, skipped the Sirius Satellite Radio at The Glen — held the day after his father's death — to attend the funeral.
In the weeks following his death, Sterling negotiated a ride with MB2 Motorsports for the 2006 season. When that team lost access to its existing car number, Sterling requested the No. 14 as a way of honoring his father's memory. MB2 was granted the number, and Sterling ran it for the remainder of his tenure with the team. The No. 14 was later taken on by Tony Stewart for his own race team, though Stewart chose the number to honor A. J. Foyt rather than as a continuation of the Marlin tribute.
Coo Coo Marlin's career represents the experience of the regional short-track champion of his era — a driver who achieved real excellence at the local level and competed respectably on the national stage without the resources to mount a genuine championship challenge.