31116-ZY3-000 Flywheel Boss - Overview. The 31116-ZY3-000 Flywheel Boss is a critical component in Honda marine engine systems. It supports the mechanical connection between the engine's rotating flywheel and the marine engine components, facilitating efficient power transfer essential for reliable engine operation. As a part designed specifically for Honda marine engines, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. The Flyw