2 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 shaft line area. Its main function is to concentrate galvanic corrosion on itself, preserving the propulsion shaft—generally made of stainless steel or bronze—against the electrochemical attack produced by immersion in salt or brackish water. Being in direct contact with the shaft and continuously submerged, this sacrificial collar absorbs degradation that would otherwise affect high-cost structural parts such as the shaft itself, the stern tube or the stern bushing. Its correct installation and periodic replacement are essential to maintain the mechanical integrity of the transmission system and avoid vibrations, looseness or catastrophic failures in navigation.

When to replace this part?

The clearest indicator that the shaft collar needs to be replaced is a visible reduction in its mass: when the anode has lost approximately 50% of its volume, it has reached the limit of its useful life and must be replaced before it stops protecting effectively. In areas with high water conductivity or boats with electrical installations of certain consumption, wear can occur in a single season, so it is recommended to inspect the collar at each docking or seasonal maintenance. Replacing the shaft collar preventively is the most economical measure to prevent corrosion of the drive shaft, a failure that may require complete replacement of the shaft and associated bearings.