Stuffing Box/Stern Gland Leak

[Bluewater2]

My new-to-me 1984 MT 34 Sedan, with a Lehman 2715E (3,400 hours), has suddenly developed a leak (drip every 3 seconds or so while shaft not rotating). The drips are coming from the (coupling?) that is forward of what I believe is the stuffing box.
Any suggestions of why and how to remedy? All thoughts and recommendations gratefully received....

 

[STB]

I think that "coupling" is the stuffing box, compressed by loosening the two jam nuts (top) on the studs, tightening up the adjustment nuts on the stud to lower the "hat" compressing the packing, and then retightening the jam nuts. Small picks and hooks and corkscrew like devices are used to extract the old packing.

If it is already adjusted all the way compressed, or is taking too much pressure to stop the leak, it need to be repacked by loosening both pairs of nuts, removing that top, removing and replacing the old packing, and retightening. It is easiest and safest done out of the water, but some will report successfully doing it in water, in some cases by packing the joint with wax or other outties from the outside first, and in some cases just by letting letting pumps manage the water while working.

Looking at that picture, I can't see well enough 5o see how much adjustment there is left.

If the shaft is pitted, which can happen if the boat was left for a long time without running, or scored, which can happen if it was over tightened, it may not be possible to get a perfect seal. Sometimes it is possible to cut or lengthen that hose a but to shift the location of the seal to an uncorroded area.

There are different choices of packing from systems that use, in our, a moldable putty, to materials impregnated with more modern lubricants. The size of the packing varies with the box, so you probably want to buy a few sizes and see which works.

There are great videos on YouTube that show all of this.

Hope this helps!

 

[ghost]

Doesn’t look like it’s been touched in awhile, though that’s hard to judge. As noted, that Is the stuffing box. You can tighten it if you don’t trust your bilge pump, but I would not run it after doing so. Old packing gets hard and can score if you tighten it. Repacking is pretty easy, especially since you have good access.

Do a search for the procedure. Go to the marine store and get a corkscrew removal tool, pull out a ring and then go back and buy packing. Of similar size. While you go to the store the remaining rings are enough, but if it worries you just stuff some paper towels in there.

When you put it back together, stagger the joints on the rings and just seat them in place gently with your finger or a screwdriver. Gently. No need or want to force them in. Tighten the gland slowly. Slowly! At first, just tighten to slow the drip down to 4 or 5 drops every few seconds. Then run the boat, tighten a little, run a little more, tighten a little until you get to a couple drops a minute when running. Stop the boat and make sure the gland is not too hot to hold, warm is okay. If the gland gets hot before being nearly dripless, you have scoring or alignment issues or both. The dripping should be essentially stopped when not running,check maybe an hour after you stop once it is both cool and the packing has expanded. If you have a gland that is well behaved when stopped but leaks a lot running, that can be a symptom of bad alignment, motor mounts, worn cutlass bearings etc.. it’s very common that glands get tightened to solve alignment related issues well beyond the glands ability to work. Other than just age, that’s how packing material gets abused and it can go bad in hours instead of years.

Btw, if you have any issues removing the packing, that’s a sign the packing absolutely needed to come out. Make sure you get it all. If it comes out easily, it was likely not bad. Neglected glands can be a pain, getting the stuff out in bits at a time. Otherwise, it literally can only take about ten minutes per gland and packing itself is pretty cheap. Knowing that you have good packing, worth it.

 

[Comodave]

If it was my boat I would haul it and rebuild the entire stuffing box. Put new hose, it has to be made for a stuffing box, and new proper clamps on it. Then repack it with a modern packing like Duramax. This will require hauling but looking at the clamps and hose, that is what I would do. This is a place that I would use T bolt clamps, not screw clamps. The one T bolt clamp looks like it is bottomed out. The screw clamps are way to long and have nasty tails on them. With it hauled you can replace the packing and not be stressed about the water flowing in. The photo is one of mine after I rebuilt the stuffing box. But I did replace the bonding wire from the front of the box with one a bit longer so I could secure it so it doesn’t flap around.

 

[Bluewater2]

Gkesden, ghost, and comodave - many thanks for your detailed responses. Very reassuring as I am not familiar with the set up on this trawler - I have spent my sailing life carrying lots of packing and two large pipe wrenches for the traditional stuffing boxes on our various boats. And I could usually re-pack while in the water. Now I have to decide if I can mess with this one while in the water or have to haul specifically for this job...............

 

[Comodave]

Since it is new to you, obviously you don’t know how old the stuffing box hose is. It looks pretty old. I would bite the bullet and rebuild the whole thing. The bronze plate, with the double nuts, closest to the transmission is where you adjust the packing. Take the double nut off and then tighten the first nut and it will tighten up the box packing. Take both nuts off and the bronze plate will slide towards the transmission. Then you can pick out the old packing in order to install the new packing. I used a drill bit to find out what size the packing was. I like Duramax packing. You can get it tight enough so that there is no dripping at all and not overheat the box. But since the hose and clamps look so rough, I would just replace them completely. At the very least get rid of the screw clamps and go with properly sized T bolt clamps. I like AWAB T bolt clamps. They don’t have any welds to promote rust and are all 316.

 

[ghost]

I’m pretty squarely in Commodave’s camp. When you renovate a system, it’s nice to do it tip to tail, not piecemeal. Personally, I’d replace the packing without delay, no reason not to. Then do everything else as soon as your next haul out. Though I do like to consider the system here to be “running gear”, not just packing gland, so that would mean new cutlass bearings (usually a safe bet they are old), checking the shaft, renewing the props, check and replace motor mounts and a good alignment. Do that and good chance you won’t have to give anything in the system attention for at least a decade, or until you hit something!