Marr competed in several non-Championship races, with his best results including winning the 1955 Cornwall MRC Formula 1 Race and finishing fourth in the New Zealand Grand Prix the following year.
Marr competiu en varias carreiras fora do campionato, cos seus mellores resultados, incluíndo a vitoria na Cornwall MRC Formula 1 Race de 1955 e terminar cuarto no Gran Premio de Nova Zelandia ao ano seguinte.