Pete Ward of Wilmington, North Carolina, asks:
"The packing in my stuffing box has become so tightly compressed on the shaft that when I put the transmission in gear, the whole thing turns in the rubber hose that’s connected to the pipe going through the hull. I’ve tried to get all the old packing out with a hook, but it’s still there. I don’t want to use a hammer. Can I use something like muriatic acid or heat to get it out?"
Don Casey replies:
This is a classic case of what can happen when the nut on the stuffing box is over-tightened. Not only does the compression exclude the necessary lubricating water, over time it also compresses the packing into a hard mass that is capable of scoring the shaft. This is why stuffing boxes should always drip slightly when the shaft is turning.
Your situation is serious, because the hose might tear or the stern tube could be damaged, in which case you could have a catastrophic leak. The only remedy is to remove every bit of the old packing from the box. A corkscrew-like tool called a flax packing extractor (#137620 westmarine.com) is inexpensive and a good place to start. However, if the packing is especially recalcitrant—which it sounds like yours might be—I’ve had good luck clamping a shark hook in a pair of locking pliers to make an extraction tool.
If you have room to do so, threading a long, thin screw into the packing and then pulling it out can also work wonders. Don’t use acid or heat, because of the potential risk to the shaft, hose and hull. Stick with poking, prying and doing whatever else is necessary to break up and dig out all the old packing.
If the boat is out of the water you might unclamp the box from the hose and try twisting it against the locked shaft. You may even be able to slide it to a more accessible position. When the box is completely empty, put in new packing and install it in rings, not in a continuous spiral. Most boxes will accept three rings with the end seams staggered at 120-degree intervals. Tighten the packing nut until you stem the flow of water. Then run the engine and adjust the nut until you get about three drops of water per minute.