US Patent 7387553 Marine drive unit overmolded with a polymer material

A marine propulsion system drive unit is provided with a polymer layer to protect its outer surface from abrasion and corrosion. The polymer layer is injection molded around the outer surface of a metallic gear case structure or drive shaft housing to provide a coat which is approximately 3 millimeters thick and which will resist scratching and corrosion. The polymer layer can be a glass filled polymer or a carbon filled polymer. An adhesion promoter can be used to enhance the bonding and intimate contact between the inner surface of the polymer layer and the outer surface of the metallic gear case structure or drive shaft housing.