TURBOCHARGER GROUP 4N9541 - Caterpillar

If the vessel cannot continue under its own power, it is recommended that the vessel be towed. If pressurized oil cannot be supplied to the marine gear shaft bearings while being towed, the propeller shaft must be secured so as to prevent the turning shaft (caused by the propeller windmilling through the water) from damaging the marine gear shaft bearings.
Turning of the propeller shaft without proper lubrication for long periods will damage the marine gear shaft bearings.
After the shaft has been secured, have the towing vessel travel at slow speed in order to minimize the windmilling force on the propeller. If, while the vessel is being towed and the marine gear is allowed to windmill for long periods, the engine must be started and the marine gear operated for five minutes every twelve hours to lubricate the shaft bearings.There are several ways of preventing shaft rotation; the correct method depends upon the turning force of the propeller, and the construction of the propeller shaft tunnel. Use the method best suited for the type of installation.Propeller Shaft Wrapping
1. On small vessels, wrap a heavy rope around the propeller shaft. The number of wraps needed will depend upon the mass of the propeller and propeller shaft.2. Secure the rope in the opposite direction of shaft rotation.Securing Companion Flange
1. Remove one or more bolts from the companion flange coupling.2. Bolt a chain to the companion flange.3. Wrap the chain several times around the propeller shaft.4. Secure the loose end of the chain at a right angle to the shaft and in opposite direction of shaft rotation.