Sierra parts are machined to perfectly match the OEM part they replace, which gives trained technicians and DIY mechanics the confidence they need when making necessary repairs. Parts are also designed specifically to be of marine-grade quality to resist corrosion and provide reliable operation for years.18-0172 Applications:• Mercury Mariner: 10525418 Reliable construction resists corrosion For Mercury Mariner engines | Sierra Oil Seal For Mercury Mariner, Part #18-0172