13421-ZW5-000 Balancer Shaft Cvr - Overview. The 13421-ZW5-000 Balancer Shaft Cvr is an essential cover component within Honda marine engine systems. It plays a critical role in protecting the balancer shaft by shielding it from debris, corrosion, and environmental wear, ensuring the engine maintains smooth operation and long-term reliability. Designed to integrate seamlessly with existing marine engine parts, it maintains optimal performance and durability.. Key Features. Precisely manufactured