3 AXLE COLLAR

Function and technical context

The shaft collar is a cathodic protection component that is installed directly on the boat's drive shaft, acting as a sacrificial anode in the drive shaft area. Its mission is to concentrate the galvanic corrosion on itself, preserving both the shaft and the other submerged metallic elements—propeller, horn and bearings—against the electrochemical attack of salt or brackish water. Without adequate cathodic protection on the shaft, corrosion advances silently on higher-value components, potentially compromising the structural integrity of the shaft and causing clearances in the stern tube bearings that lead to vibrations, loss of propulsive efficiency and even water entry into the hull.

When to replace this part?

The main indicator that the shaft collar needs to be replaced is the visible loss of mass: when the anode has consumed between 50% and 70% of its initial volume, it has ceased to offer sufficient protection and must be replaced immediately. It is recommended to inspect it at each beaching or, at least, at the beginning and end of each navigation season; In waters with high conductivity or in vessels with a higher density of electrical equipment on board, the inspection should be more frequent. Replacing the collar preventively is the most economical measure to avoid severe damage to the drive shaft, the horn or the transmission assembly, repairs that may be unfeasible on the high seas and very expensive in the workshop.

Compatibility table