Mercury - Magnesium Transom Bracket Anode Corrosion Protection Magnesium 8M0179781. Overview. If you spend your seasons exploring quiet freshwater coves or easing your big V12 out of the marina at first light, you know how much trust you put into the hidden parts of your outboard. Corrosion might not be something you see every day, but it's always working in the background-and protecting your engine from it becomes part of the rhythm of responsible boating. The Mercury Magnesium Transom Bracket