When your boat is hauled, a thorough inspection of all running gear is essential to the proper performance and reliability of your vessel. One key component of the running gear to pay special attention to are the cutlass bearing(s). It is important to check the play in the cutlass bearings and renew them if needed. A common question is “When are new bearings actually needed and what is the proper method of determining when they are needed?” The cutlass bearings clearance to the shaft should be checked using a feeler gauge or dial indicator to determine the existing clearance between the shaft and the bearing materials. A two-inch shaft has the tolerance of a .006″ minimum to a .012″ maximum.
Unfortunately, new bearings alone are not always the answer. Shaft wear can cause a new bearing right out of the box to be out of tolerance. Shaft repairs are expensive but are required if we are to ensure peak performance of the running gear. In many cases, shaft tolerances are not as critical as the example we have provided here. High-speed performance vessels are more prone to vibration issues that may be caused by excessive bearing clearances such as sport fishing vessels that strive to achieve maximum efficiency and the least amount of noise possible. Slower speed vessels, such as cruisers and trawlers, can perform satisfactorily with higher clearances.
Never operate your vessel with a continuous vibration. The vibration can cause many more serious issues. Sport fishing vessels that strive to achieve maximum efficiency and the least amount of noise possible should adhere to recommended tolerances.