Mamby meraih gelar juara kelas welter ringan Dewan Tinju Dunia dari petinju Korea Selatan, Kim Sang-hyun, Pebruari 1980 dengan menghentikannya pada ronde ke-14 di Seoul.
Mamby won the World Boxing Council light welterweight title from South Korean Kim Sang-hyun in February 1980 by stopping him in the 14th round in Seoul.