Stuffing Box Maintenance

It happens every spring: Right after launching their inboard-engine-powered boats, owners are left wondering why they didn’t repack the engine shaft seal packing gland, also known as a stuffing box, during the off-season.

The stuffing box prevents (most) water from entering the hull while still allowing the propeller shaft to turn. The beveled glands force packing material against the shaft as the unit is tightened. A dedicated stuffing box wrench with straight jaws, like the one shown, is good at getting into cramped spaces.
The stuffing box prevents (most) water from entering the hull while still allowing the propeller shaft to turn. The beveled glands force packing material against the shaft as the unit is tightened. A dedicated stuffing box wrench with straight jaws, like the one shown, is good at getting into cramped spaces. Doug Logan photo.

It must be the drip, drip, drip torture you endured all last season as you anxiously watched the old seal leak a little too fast for your liking, the flax packing material having sacrificed itself as it is supposed to do. Now that it’s old and used up, water is filling the bilge, and numbing your mind as you constantly think, “I have to remember to repack that when I have the boat out of the water next time.”

It is possible to repack the gland with flax sealer while the boat is in the water, but don’t try it.  You run the risk of sinking your boat, particularly if you’re not experienced at performing this task.

So, as we come to the end of another summer and you start to think of hauling the boat for the winter, why not put the job of repacking the stuffing box at the top of your list of haul-out and winterization projects? That way you won’t forget it in the spring rush and endure another season of kicking yourself while the bilge fills up with water and the bilge pump works overtime to keep up.

There are different kinds of packing materials like the standard flax version (top) or the Teflon/ PTFE type below.
There are different kinds of packing materials like the standard flax version (top) or the Teflon/ PTFE type (bottom).

The chore is easy enough, with a little penetrating oil, a couple of pipe wrenches or a dedicated stuffing box wrench, a pick or corkscrew for removing the old worn out packing material , a small wire hand brush, a few rags,  and ten bucks’ worth of flax sealer. You can change the packing with about half an hour of labor—half of which is waiting for the penetrating oil to work. Usually the hard part is contorting yourself into the engine space to do the work.

There are different types and sizes of packing available. Some have Teflon or graphite added for improved lubrication. Do not use graphite on bronze shafts because it can cause galvanic corrosion of the shaft. Visit Western Pacific Trading, a major distributor of packing materials, for descriptions of the different types. You’ll need to know what size packing to buy (5/16″, 3/8″, etc.) and the easiest way to to that is to measure the size of the old packing, taking wear and compression into account. (This is another good reason not to try to do this job in the water.)

Here are my step-by-step instructions for repacking your stuffing box.

  • Lightly wire brush any corrosion off the stuffing box nuts.
  • Throw a rag over the transmission where the shaft connects to it so that you don’t get any penetrating oil on the transmission seals when you apply PB Blaster or other penetrant to the stuffing box.
  • Carefully apply penetrating oil to the stuffing box nuts and wait 10- to 15 minutes.
  • Using pipe wrenches or a stuffing box wrench, loosen the lock nut, then the female packing nut that holds the flax material. The nuts should loosen by turning the wrenches outboard and away from each other. In other words, the locking nut loosens when you turn it to the right as you look aft — you’re moving it away from the packing nut by advancing it along the threads. Note: use wrenches, not plumber’s pliers: You’ll be able to get the right torque and not gall the nuts by using proper wrenches.
  • Pick any old flax sealer out of the female packing  nut. You can use a pick or corkscrew. Follow with a 3M (not metal) kitchen scouring pad to clean the threads. Don’t use a tool that will gall the threads.
  • Inspect the rubber hose and clamps that connect the stern tube to the stuffing box. Replace as necessary using only 6-ply stuffing box hose (not exhaust hose).
  • Inspect the shaft and clean with emory cloth as needed.
  • Install the new flax seal. Most packing nuts will take three coils of new packing material. Make sure that at least four threads are showing on the nut for it to grab securely.
  • Cut the three coils of flax to circle the shaft exactly. Cut the ends at 45-degree angles so that they overlap when they meet instead of butting vertically.
  • Coat the packing coils with the green packing paste provided. I am not in favor of other packing greases some people recommend because many of these products contain graphite.
  • Seat the coils of flax seal in the nut, tamping them down with a blunt tool to avoid cutting or fraying the flax seal.  Each ring should have its end cuts offset from the layer below.
  • Tighten the packing nut until a very little bit of resistance is felt. Do not over-tighten! You should adjust the nuts again when the boat is in the water so you get the drip-rate right. Before the final adjustment run the engine in gear, allowing the seal to take a set (the packing nut should still be cool or just warm to the touch, not hot. You should be able to put your hand safely on the nut. Remember, the idea is lubrication, so if it’s  hot to the touch it’s probably too tight. At the same time, it should not be leaking copiously — just a steady drip.
  • Go slowly in tightening the seal, say a half turn of the packing nut at a time until it’s just right. Again, avoid over-tightening as the flax will take a set, and backing off it won’t work as well as slowly adjusting it.
You can use a 3M kitchen pad (not metal) to help scour out the threads of the packing nut. Doug Logan photo.
You can use a 3M kitchen pad (not metal) to help scour out the threads of the packing nut. Doug Logan photo.

Again, a stuffing box should drip at a regular, albeit slow rate of between two and six  drops a minute with the shaft turning. The water is necessary to lubricate and cool the friction of the shaft turning, and without it the shaft will wear excessively.

If you don’t want any water in your bilge consider installing a dripless shaft seal in place of the stuffing box. A dripless seal will cost more, requires that the shaft be pulled to install, and still needs occasional adjustment. I’ll go over installing a dripless shaft seal in a future blog. For now, be happy water is dripping in at a controlled rate, and the stuffing box is working as it should.


Boat Trailer Maintenance

A third of the 100,000 plus boats for sale on this website are listed with trailers. That’s no surprise because according to BoatUS, nearly 7 million Americans own a boat with a trailer. Most likely, you’ve seen some of those boaters pulled over on the side of the road with trailer problems–wheels off, axles broken, people in a state of frustration and panic as their prized boat hangs in the balance over a broken down trailer. If you are like me, you’re first reaction is, “Oh, that poor slob, I’m glad that’s not me.”

Most boats under 25 feet are trailerable.

Truth be told, not enough of us pay enough attention to the condition of our boat trailers. Following a few simple tips on maintenance can reduce the possibility of that breakdown on the side of the road.

Top Five Causes of Boat Trailer Service Calls

The top five reasons for service calls to the BoatU.S. boat trailer roadside assistance program are:

  • 44% – Flat Tires
  • 20% – Wheel Bearing Failures
  • 14% – Axle Problems
  • 9% – Suspension Problems
  • 5% – Tongue/Coupling Trouble
bearing buddy
Bearing Buddys are spring loaded hubs that constantly force grease into the bearing

Trailer or ST tires are different from car tires—they’re usually of a bias ply design, which provides higher load capacity and stiffer sidewalls compared to the more flexible radial tire design found on most passenger cars.

Under inflation is the prime cause of trailer tire problems. An underinflated trailer tire won’t sag like your car’s tires because of its stiff sidewall construction. Tires may look normal, but only a pressure gauge can accurately show proper inflation. You can’t eyeball it! Check your tire pressure with a tire gauge.

Oxidation is often the next culprit for trailer tire failure. Trailer tires need to be replaced every 3–5 years of use, even though they usually appear to have plenty of tread left. Trailer tires often sit in one spot for weeks, if not months, subject to UV radiation. Is it any wonder that the deteriorated sidewalls blow out under pressure? Check for dry rot and crazing on the sidewalls.

Wheel bearing problems
Boat trailers are regularly immersed in water–often in corrosive salt water. Even fresh water will cause the wheel bearings to rust if not properly packed with lubricant.  Very few owners check the lubrication of the hubs and bearings as often as they should (like before every road trip). Even if they do, they don’t always use the right lubricant. Fill the hubs completely with a multipurpose No. 2 grade lubricant.

One solution is to use a spring-loaded hub, such as Bearing Buddy, that constantly forces fresh lubricant into the wheel bearing. Some models of Bearing Buddy even have a visual exterior reference to show you at a glance if there is enough lubricant in the hub. I’ve personally installed these on my own trailer and recommend them.

Even trailers not immersed in water are subject to bearing corrosion. Condensation will be sucked into hot hubs as they cool if they are not completely filled with lubricant, causing rust and pitting. The only solution is to be vigilant about lubricating your wheel bearings.

trailer rust
Axle and suspension problems may be due to corrosion but are just as likely to be from overloading

Axle, suspension, and tongue/coupling problems
Assuming your trailer has passed a visual inspection for rust and corrosion, the most likely cause of axle, suspension, or coupling problems is overloading. Another common cause is not following safe towing techniques.

Inspecting Your Trailer
Have you ever noticed that trailers stranded on the side of the road tend to have more than one problem? For instance, trailers with inoperative lights are also the same ones that have not been inspected or maintained for other, more serious problems. Before you trailer your boat, always perform a walk-around inspection.

  • Check your tire pressure with a tire gauge.
  • Check for dry rot and crazing on the sidewalls.
  • Grease wheel bearings with No. 2 grade lubricant before every trip (Don’t mix grease types).
  • Check your lights.
  • Visually check for rust and corrosion

Prudent trailer owners should carry a spare tire, a grease gun, and tire gauge. When not in use cover trailer tires with covers like you see on RV’s. If you follow these trailer maintenance tips, you’ll greatly reduce the odds of being that “poor slob” stuck on the side of the road.

Engine Starter Woes or Click, Click, Nothing!

It is the middle of the night, and we’ve been sailboat racing offshore for 14 hours so the batteries are draining down. We decide to start the engine to charge them up—click, click, click, uh oh!  That dazed feeling that you might be in trouble begins to set in, and you try to figure out what is wrong.  It’s just two of us aboard in this year’s annual double-handed distance race out of Newport, Rhode Island—the Solo/Twin.  We are in the open Atlantic Ocean, miles east of Block Island.  Fortunately, this is a sailboat, so we aren’t marooned, but we do need batteries for all our navigational instruments and running lights, and we don’t have much juice left.

Small diesel engines like this Yanmar are often found in cramped quarters on sailboats, making access the biggest deterrent to maintenance or repair.

I stay on deck and continue to sail while my buddy Jeff pops below.  “Try it again,” he shouts—click, click, nothing.  We start shutting down all the non-essential electronics, just like Tom Hanks in the movie Apollo 13, until only the masthead running light is left working off the backup battery.  We can hear the click and see the lights dim when I hit the starter button, so we’re thinking it’s either too low a battery, a bad solenoid, or maybe even a fried starter.

Out comes the battery jumper pack, nothing. We open the compression valves on the engine and spin it by hand, so we know the engine isn’t frozen, but still we can’t get it started.  I’m remembering all those horror stories of people breaking an arm trying to start a diesel by hand as the handle spins out of control, especially in our cramped sardine-can-sized engine compartment, and I’m thinking how much worse this might be if one of us were injured on top of our present dilemma. Jeff starts banging on the starter with a winch handle as I try the starter button again.

We finish the race about dawn, still with no engine, so we sail the boat right to the mooring and tie up.  Exhausted, we try to think through all the possibilities of the engine problem once again.  We had spark but were afraid of trying the age-old solution of touching a screw driver across the contacts of the solenoid, due to the confined space and having a hand in the engine compartment if it did decide to fire.  So we go ashore in search of a new starter and solenoid, sure that one is the answer.

After a shower and a short nap we return with a brand new starter/solenoid and install it, click, click nothing.  But we’ve also brought a jumper wire from Jeff’s basement that sparks enough for him to pull his hand out of the engine compartment super-quick.  The problem turns out to be the contact starter switch.  A $9 part at the local Auto Zone.  We re-install the old starter and return the unused new starter before picking up the contact switch.

Jeff has since admitted that he had been having problems with the switch for over a year; previously you had to push it just right to start the engine. It was making contact, just not enough to kick the starter over. Ah engine maintenance! Left alone, a simple $9 switch will wait to cause trouble only when it can create an adventure for you.