90452-GK4-600 Plain (5mm) Washer - Overview. The 90452-GK4-600 Plain (5mm) Washer is an essential fastening component within Honda marine engine systems. It serves as a simple, flat metal ring designed for fastening or spacing applications to ensure the reliable operation of various marine engine assemblies. Engineered to meet precise factory specifications, this washer plays a crucial role in maintaining optimal mechanical stability and performance.. Key Features. Type: Plain Washer, 5mm thickn