40103-ZW5-000 Case (Lower) Seal - Overview. The 40103-ZW5-000 Case (Lower) Seal is a critical component in Honda marine engine systems. This seal is designed to protect the lower unit case by preventing water, debris, and contaminants from entering the engine casing, ensuring seamless operation and enhanced longevity of the marine engine. As part of the sealing system, it plays an essential role in maintaining a watertight environment that safeguards internal engine components.. Key Features. Pr