Volvo Penta Magnesium Cavitation Plate Anode for SX from 2007 onwards and DPS OutdrivesIf your anode is worn away by 33% or more, it is advisable to change it, as more of its surface area has been worn away and the remaining anode will wear away much quicker. The magnesium version is only suitable for freshwater, aluminium is suitable for brackish/salt water and Zinc for saltwater.Volvo Penta Part No: 3888815For: SX-A from 2007 onwards, DPS-A, DPS-B