The packing material encircling your shaft and tucked out of sight inside the packing nut is truly your boat’s Achilles heel. Installed improperly it can damage the prop shaft or even sink the boat. Getting it replaced at least biennially should be on your list. On a mid-size cruiser it’s a job that ranks just below rebuilding the head— not fun. (PS contributor Rod Collins has a good step-by-step illustration of the process at www.marinehowto.com.)
We recently went about the task of replacing the packing aboard our Bristol 35.5 centerboard test boat. She’s powered with a 40-horsepower Yanmar 3JH3, and the shaft has a brass packing nut just forward of the stuffing box. When the boat’s in the water, the packing gland drips the prescribed once or twice every three minutes, keeping the waxed felt moist, which keeps seawater on the proper side of the hull. We’ve heard of intrepid souls replacing their packing material while the boat is in the water. We’d like to discourage that idea, particularly aboard boats with compromised access to this typically hard-to-reach space. Too much can go wrong. Wait until the boat is on the hard where you can blaspheme your way into a proper installation.
First, avoid the cheapie corkscrew packing extractors you get from the big box stores. The corkscrew is intended to grab the felt and pull the packing out. The cheap extractors are crimped onto the flexible handle, and most of the time a recalcitrant bit of packing will entail a hard pull that separates the corkscrew from the handle—as happened to the $12 extractor we bought at a big box retailer (see photo 1, above).
Enter my new Palmetto 1117 Packing Extractor Set. Savoring the mouse-over magnification of the images on Amazon, I could see that the corkscrew is threaded into the handle (no crimps!) and the set also came with a set of screw-on wood screws to embed in hardened packing that refused to budge. In addition, the Palmetto Packing Extractor Set comes with three sizes of long-handled picks, and a small open-end wrench that allows you to rotate your tool of choice into the old packing. My Palmetto 1117 Packing Extractor Set is absurdly priced at $162.39, but we’ve yet to find a high-quality tool at the bottom of a discount bin.
The distance between my drive shaft and the interior wall of the packing nut is approximately a quarter inch, and the smallest corkscrew fits into this space handsomely. Mind you, we are operating in the engine space through the access panel in the quarter berth. I had the shore power hooked up through an AC adapter so I had the battery charger on, a small space heater plugged into an outlet and engine-room lights. I also used a headlamp, which has become part of my wardrobe during spring commissioning.
It’s a hellish squeeze around the exhaust elbow. You’re operating mostly one-handed and instead of pulling the material out toward you, you’re actually pulling it away from you. Leverage is severely limited by the fuel tank.
Palmetto has obviously seen this movie. The picks come in handy in one very important way. If you can get the tip of the pick under a turn of the corkscrew, it’s possible to lever the corkscrew and the packing up and out. I silently thanked Archimedes for this flash of inspiration. There were two layers of packing inside my packing nut and the second, deeper one came out laughing.
Now to reinstall fresh packing. I took a look at the sundered remnants of my old packing and couldn’t tell if it was a quarter inch or five-sixteenths. Happily, I had both sizes in inventory and after a bit of fussing I decided the quarter inch was going to work. I had some packing grease, and slapped some onto the shaft before the installation. There is an important feature of re-installing packing you need to be aware of.
There will be a small gap where the ends of packing meet inside your packing nut. Make sure the small gap of the second layer is on the side opposite the small gap of the first layer. This will deny sea water a clear path inside the boat. Hand tighten the packing nut back onto the shaft collar and you’re back in business.