Donahue died in Santa Monica after suffering a heart attack.
His role as Sandra Dee's young lover in 1959's "A Summer Place," made him a teen matinee star. Donahue went on to star in a series of teen romances, including "Parrish" (1961), "Rome Adventure" (1962) and "Palm Springs Weekend (1963).
Born Merle Johnson Jr., the New York City native moved at age 19 to Hollywood, where he was discovered by Warner Bros. He was given his screen moniker by Henry Willson, the same film agent who named Rock Hudson.
During his heyday, Donahue split his time between the movies and television, appearing in the detective series "Surfside Six."
He had a bit part in 1974's "Godfather, Part II," playing a character named Merle Johnson. But with his career in decline, Donahue began abusing drugs and alcohol, even spending a summer homeless in New York's Central Park.
He became sober by the early 1980s and has had bit parts since then, including in director John Waters' 1990 film "Cry-Baby."
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