Mercury - Magnesium Anode Kit MR & Alpha One Series Freshwater Protection 888755Q04. Overview. If you've ever eased out onto a glass-calm lake just after sunrise, you know that feeling of wanting everything on your boat to work exactly as it should. No surprises, no worries - just smooth water and a drive system you don't have to think twice about. The Mercury Marine part number 888755Q04 Magnesium Anode Kit delivers that kind of confidence for owners of older MerCruiser MR and Alpha One drives.