COLLARIN EJE 35mm. STD (ZN)

Function and technical context

The 35 mm shaft collar in standard size is a retaining and sealing element that works directly on the tail shaft of the boat, acting as a support and stabilization point between the propulsion shaft and the horn or stern bearing. Made of zinc (ZN), it also fulfills a galvanic function, protecting the metal shaft against electrolytic corrosion produced by the potential difference between different metals submerged in salt or fresh water. Its correct installation guarantees that the shaft rotates without excessive vibrations, maintaining the alignment between the engine and propeller, which has a direct impact on the efficiency of the propulsion and the integrity of the adjacent seals and bearings. If the collar loses its fit or degrades, the shaft is exposed to accelerated corrosion and clearances can appear that compromise the entire drive train.

When to replace this part?

The most common symptoms of a deteriorated shaft collar are the appearance of unusual vibrations in the hull during navigation, noticeable play in the shaft when moved manually, or visible signs of pinpoint corrosion in the area of the shaft protected by the part, indicating that the zinc has been completely consumed and has left the base metal exposed. As it is a component of galvanic sacrifice and mechanical retention, it is recommended to inspect it at each annual beaching and replace it when the zinc shows wear greater than 50% of its mass or when cracks, deformations or loss of fit on the axis are observed. Replacing the collar preventively every nautical season is the most recommended practice by specialized workshops, since the cost of the part is minimal compared to repairing a corroded shaft or replacing bearings damaged by poor alignment.