Cavitation and vibration caused by poor A bracket shape. Hull surface pressure and vibration measurements carried out during sea trials on a small twin-screw coastal ferry indicated that the shape and positioning of the A brackets, together with the design of the propeller, were likely to be the main causes of unwelcome cavitation activity on the propeller blades and consequent levels of structural vibration. In this case levels of 125 mm/s on the after deck were regularly being reached.

A wide range of rudder or steerable duct actuating force, cavitation and integrity problems can occur from time to time. In the case of rudders, these may take the form of bearing failures or erosion of the rudder plating, the latter due either to cavitation developed by the rudder itself or from the cavitation entrained in the helical slipstream from the propeller. Steerable ducts can also have accentuated vertical seaway loadings and, in common with fixed ducts, can suffer from erosion on their inner plating.

The ship was alongside in port when the main engine was started, and the oil mist detector gave a warning alarm. When opening up the crank case a hot crankpin bearing was found. The crankshaft
was found to be seriously damaged in way of one crankpin, causing the vessel to be put off hire for more than a month before resuming operation.