A 6' 8 center from West New York, New Jersey, Mahnken played basketball at Georgetown University during the early 1940s, earning All-American honors in 1943.
A 6' 8 center from West New York, New Jersey, Mahnken played high school basketball at Memorial High School in his hometown. He played at Georgetown University during the early 1940s, earning All-American honors in 1943.