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. Big directional pump is for big block GM engines with stamped steel timing covers. 18-3577-2 Applications:• Crusader: 67859, 17670, 30109, 811573• GM: 6269358• Mercury: 811573, 8504541, 46-8M0113735, 17670, 67859, 59972, 54534, 49139, Fl1100997, F6269358, Fl1101053, 850454002, 850454, 878342• Mallory: 9-42604• OMC: 3854118, 3855991, 0983296, 0986074, 0987447• OMC Inboard: 6269358• Volvo: 3855991, 856609• GLM: 15301• Pleasure Craft: RA057019• Pro Marine: 64454• Redline: RL3577 Reliable construction will resist corrosion For Mercruiser/OMC engines | Sierra Circulating Water Pump For Mercruiser/OMC, Part #18-3577-2