Sierra 18-6011A Aluminum Anode Sierra replacement aluminum anode. Aluminum anodes are recommended for boats in brackish water, or if a boat is used in both fresh and salt water environments. Fits Most MercuryMariner OBs 35hp above and all MerCruiser except Bravo Interchangeable with Honda Outboard 41107-ZW1-003ZA Mercruiser Stern Drive 31640 316404 31640A1 97-31640Q4 Mercury Marine 31640 316403 316404 31640A1 31640A2 31640A4 31640B4 72436A1 97-31640Q4 Tecnoseal 00800AL 01411AL California Reside