COLLARIN EJE 25mm. STD (AL)

Function and technical context

The 25 mm shaft collar is an axial positioning and retention element that works directly on the transmission shaft in boat propulsion groups. Its main function is to maintain the shaft in its correct longitudinal position within the stern tube or bearing, avoiding unwanted displacements that would compromise the alignment between the propeller and the engine. Made of aluminum, it offers an optimal relationship between lightness and resistance to marine corrosion, being especially suitable for installations in salt or brackish water. A worn collar or one with excessive clearance can cause abnormal vibrations in the shaft line, accelerated wear of the stern seals and, in serious cases, water entering the interior of the hull through the stuffing box.

When to replace this part?

The most common symptoms of a damaged shaft collar are noticeable axial play when manually moving the shaft, vibrations or rattles at certain revolutions, and premature and irregular wear of the stuffing box or stern seal. It is recommended to inspect this component during each seasonal maintenance and replace it whenever deformation, cracks, active corrosion or play out of tolerance is observed. Replacing the collar preventatively during a scheduled grounding is significantly more economical than dealing with a shaft failure or a water leak while underway.