MERCURY TAIL ANODE 42121A2 CM42121A2

Function and technical context

The tail anode is a cathodic protection component that is installed in the aft area of the outboard motor, acting as an electrochemical sacrifice against galvanic corrosion in salt water. Its function is to absorb corrosion that would otherwise damage critical engine parts such as the block, propeller blades and internal cooling systems. Being directly exposed to seawater, the anode preferentially oxidizes, protecting the rest of the metal structure of the engine. Without this element, the salinity of seawater would accelerate the deterioration of aluminum and steel components, compromising the tightness and durability of the engine.

When to replace this part?

The tail anode should be inspected at the end of each boating season and replaced when significant material loss, accelerated erosion, or partial disintegration is observed. Although there is no set range in operating hours, anodes typically become depleted after one or two full seasons of use in salt water, depending on the salinity and electrochemical activity of the environment. Preventive replacement is the most economical measure, since changing the anode before it is completely consumed avoids costly repairs due to advanced corrosion of internal engine components.

Compatible Mercury Mariner Engines

Equivalent manufacturer part numbers