He drove in the USAC Championship Car series, racing in the 1961–1964 seasons, with 49 career starts, including each Indianapolis 500 contest in that span.
Marshman, driving a Lotus 29-Ford, extended his lead until the 37th lap, when he was forced off the track to avoid hitting a slower car driven by Johnny White.
An embarrassed and crestfallen Marshman replied, "I thought if I bought it no one would know I was a driver and they wouldn't ask me silly questions."
When his Lotus-Ford crashed into the west retaining wall and ruptured the fuel tank, he was not wearing fire-retardant clothing to protect him according to some reports.
[3][4][5][6] About a year after her husband's death, Marshman's widow, Janet F. Marshman, sued Ford Motor Company for $5 million, claiming that the crash resulted from negligence by the car owner, purported to be Ford, which also failed to comply with a warranty that the car was safe according to the suit.