12312-ZZ3-000 Head Cover Gasket - Overview. The 12312-ZZ3-000 Head Cover Gasket is a vital sealing component within Honda marine engine systems. Designed to fit precisely between the cylinder head cover and engine block, this gasket prevents the leakage of oil and fluids, ensuring optimal engine lubrication and smooth operation. As an essential part of the engine's valve train system, it helps maintain the integrity and reliability of your marine engine system by providing a tight, durable seal