91305-KC1-850 O-Ring (16.5X2.5) - Overview. The 91305-KC1-850 O-Ring (16.5X2.5) is a critical sealing component engineered for Honda marine engine systems. It supports the crankcase and gasket systems, playing a vital role in preventing fluid leaks and maintaining system integrity under demanding marine conditions. Designed to exact factory specifications, this O-Ring ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Precision O-Ring