Stuffing Box

A stuffing box, also known as a stuffing gland, packing gland or packing box, forms the seal between the propeller shaft and the hole in the hull through which the shaft passes. It is made of a threaded sleeve and a hollow nut through which the propeller shaft passes allowing the shaft to turn freely.  The nut is filled with rings of wax-impregnated material, called flax packing, and screwed into the sleeve. The packing is compressed around the smooth shaft as the nut is tightened and a little water is allowed to leak into the boat past the packing. The slight water leak serves to cool and lubricate the bearing, while the packing adjustment nut allows the flax to be tightened to adjust for wear. Over time, the seal breaks down and with repeated tightening of the nut, it will leak and the flax packing must be replaced. See Lasdrop Shaft Seals for a leak free alternative to the stuffing box.