MERCURY ANODE 47820

Function and technical context

The Mercury 47820 sacrificial anode is a passive cathodic protection component integrated into the cooling system of Mercury Mariner 20 hp marine engines. This anode acts as an electrochemical barrier against galvanic corrosion that occurs when different metals (aluminum, copper, steel) come into contact with salt or brackish water. By oxidizing preferably before the engine components, the anode protects the internal surfaces of the block, cylinder head and cooling ducts, preventing the formation of adherent oxides that obstruct water flow and compromise thermal dissipation.

When to replace this part?

Sacrificial anodes gradually corrode and lose effectiveness depending on sailing time, water salinity and operating conditions. It is advisable to inspect the condition of the anode at least once at the beginning of each sailing season and replace it when it shows more than 50% visible wear or shows signs of heterogeneous corrosion. A preventive replacement annually or every 200-300 hours of operation is the safest practice to ensure continuous protection of the engine and prevent costly repairs due to internal corrosion of the cooling system, especially when sailing in salt water or high salinity coastal areas.

Compatible Mercury Mariner Engines

Equivalent manufacturer part numbers