16805-ZY9-003 Water Separator Cup - Overview. The 16805-ZY9-003 Water Separator Cup is a critical component in Honda marine engine systems, specifically designed to filter out water and debris from fuel before it reaches the engine. This part supports the fuel system by acting as a water separator, preventing contaminants from causing damage or reducing engine efficiency. Manufactured to meet Honda's factory specifications, the 16805-ZY9-003 Water Separator Cup ensures seamless integration with