91303-MG7-003 O-Ring (13.8X2.5) - Overview. The 91303-MG7-003 O-Ring (13.8X2.5) is an essential component designed for Honda marine engine systems. This O-ring provides a critical sealing function, preventing leaks and ensuring the integrity of fluid systems to keep the engine operating reliably. Its precise size, 13.8mm inner diameter by 2.5mm thickness, matches factory specifications, allowing seamless integration with existing parts and maintaining optimal performance and durability.. Key Fea