The keys to a stuffing box's longevity are twofold. The first and most common cause of chronically leaky stuffing boxes involves the condition of the surface of the propeller shaft directly beneath the packing. If it's in any way irregular, pitted, or damaged, the packing will be torn up each time the shaft rotates beneath it, which may be as many as 1,500 or 2,000 times per minute. The pitting or damage is often caused by the stuffing box's oxygen-poor environment. If this is the case, then no amount of repacking-regardless of the type of space-age "leak-proof" material you use-or adjustment will resolve the problem. Two solutions exist: Replace the shaft, or use a longer or shorter stuffing-box hose to move the location of the packing over an undamaged section of shaft.