31116-ZY3-020 Flywheel Boss - Overview. The 31116-ZY3-020 Flywheel Boss is a critical component within Honda marine engine systems. Acting as the vital mounting point for the flywheel, it supports the mechanical motion of the engine, ensuring reliable operation and consistent engine rotation. Precisely designed to match factory specifications, this component seamlessly integrates with your Honda marine engine hardware, contributing to optimal performance and durability.. Key Features. Serves as