91301-MY9-003 O-Ring (15X2.5) - Overview. The 91301-MY9-003 O-Ring (15X2.5) is a vital sealing component within Honda marine engine systems. This O-ring serves the critical function of creating a watertight seal in marine assemblies where it is installed, preventing leaks and maintaining system integrity. As a genuine OEM component, it is engineered precisely to factory specifications ensuring seamless integration with existing parts, maintaining optimal performance and durability.. Key Features