91304-ZY6-010 Chain Case Gasket - Overview. The 91304-ZY6-010 Chain Case Gasket is a critical component in Honda marine engine systems. This rubber gasket functions as a durable seal designed to prevent leaks within the chain case, a vital part of the engine's lubrication system. By securing the chain case efficiently, it helps maintain proper lubrication and protects internal engine components from water intrusion and contamination. Engineered to fit precisely with existing chain case hardware,