BMW MARK 1 TAIL ANODE

Function and technical context

The tail anode for BMW Mark 1 is a cathodic protection element that acts as an electrochemical sacrifice in the stern drive of the boat. Its function is to attract the galvanic corrosion generated by the potential difference between submerged metals and sea or brackish water, thus preserving the noble metallic surfaces of the stern group: the casing, the shaft, the propeller and the internal components of the transmission. Without this element, galvanic corrosion directly attacks the structural parts of the propeller, causing accelerated deterioration of the aluminum and steel of the tail unit, which can lead to cracks, loss of sealing and, ultimately, serious transmission breakdowns.

When to replace this part?

Zinc anodes should be inspected at least once a season and replaced when they have lost approximately 50% of their mass, since below that threshold they no longer offer effective protection against galvanic corrosion. A clear sign that the anode is depleted is the appearance of pitting or whitish discoloration on the surface of the aluminum in the aft group, indicating that corrosion is already attacking the base metal. It is recommended to replace the anode preventively at each seasonal tune-up to ensure the integrity of the transmission and avoid higher-cost repairs when the boat is already in the water.

Compatibility table