56151-ZY1-871 Back-Up Ring - Overview. The 56151-ZY1-871 Back-Up Ring is a vital part of Honda marine engine systems, specifically designed to support sealing systems in marine environments. Its primary role is to provide support and prevent extrusion of primary seals under pressure, ensuring the longevity and effectiveness of the seal in Honda marine engines. This back-up ring is engineered for seamless integration with existing hardware and maintains optimum performance and durability in deman