Sierra 18-6024 OMC Zinc Gearcase Anode Sierra replacement anode. Interchangeable with GLM 12776 JohnsonEvinrude Outboard 393023 436745 OMC Stern Drive 393023 Fits 1982 - 1987 Gearcase Zinc is for saltwater only Magnesium is for freshwater Aluminum is for brackish water or if the boat is used in both salt and freshwater California Residents WARNING Cancer and Reproductive Harm - P65Warnings.ca.gov Other Details Google Product Type Engine Parts Product MPN 18-6024 Product UPC 030999563958 Fast Shi