SHORT COLLAR 25mm SHAFT.

Function and technical context

The 25 mm short shaft collar is an axial positioning and fastening element that works directly on the boat's drive shaft, ensuring that said shaft maintains its correct longitudinal position within the propulsion assembly. Its main function is to retain the shaft and prevent unwanted axial displacements that could compromise the alignment between the motor, coupling and propeller. As it belongs to the underwater transmission system, this component works in an environment of high mechanical stress and exposure to marine corrosion, so its structural integrity is critical to guarantee the efficient transmission of engine power to the propeller. A damaged collar or one with excessive play can cause abnormal vibrations in the shaft, premature wear of the stern tube bearings and, in severe cases, damage to the stuffing box or the shaft seal, with the consequent risk of water entering the hull.

When to replace this part?

The most common symptoms of a worn or damaged shaft collar include noticeable vibrations in the drive shaft at certain rpm, clunking or knocking noises from the horn and stuffing box area, and visible or noticeable axial movement in the shaft when performing a manual inspection with the engine stopped. It is recommended to inspect the collar at each annual docking or at each seasonal maintenance, checking the tightness, the absence of cracks and the condition of the fixing screws. Replacing this component preventively at the slightest sign of looseness or corrosion avoids more costly breakdowns in the transmission assembly and prevents risky situations in navigation.