31251-ZY3-003 Gear Assembly (Inner) - Overview. The 31251-ZY3-003 Gear Assembly (Inner) is a critical component in Honda marine engine systems. It acts as an internal gear that is essential for the transmission of power within the marine engine. Designed to meet the exacting standards of OEM specifications, this gear assembly ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Precision-engineered gear assembly designed for internal us