23173-ZY3-000 Mount Case Seal Rub - Overview. The 23173-ZY3-000 Mount Case Seal Rubber is an essential sealing component for Honda marine engine systems. This part functions as a gasket that ensures a secure seal between the engine case parts, preventing fluid leaks and contamination ingress. It supports the engine's reliability and longevity by maintaining the integrity of the mounting case system. Designed specifically for Honda marine engines, it ensures seamless integration with existing par