Warning: This post is boring!
So I have had a slow drip from the stuffing box for some time now, which I have known. Part of the reason for neglecting this was because I didn’t know where to even begin.
For those who don’t know what a stuffing box, it is the is a mechanical seal assembly used to prevent water from leaking around a rotating shaft, such as a boat propeller shaft. Some water needs to be present to cool the shaft, provide lubrication of packing material and keep it from overheating. It works by compressing packing material around the shaft using an adjustable nut, allowing the shaft to move while creating a tight seal.
The slow drip turned into a fast drip once back in the water and I knew it was time to do something about it, as my bilge was fuller than normal this morning. With the encouragement from my good friend over the phone, I started to hammer away to loosen up the locking nut and packing nut. Since the stuffing box is in an awkward tight place behind the engine I also checked off my yoga for the day. After a few hours of loosening the locking nut and tightening the packing nut, I managed to stop the leak. Tomorrow, I will run the boat in gear to make sure I haven’t tightened it too much and as a result overheat.
As soon as I think there is nothing more to learn, Sarantium throws me another opportunity to learn!
The lower nut is the packing nut and the one directly above is the locking nut, which does exactly that; blocks/locks the packing nut from moving back.
Sailaway Sarantium 
Not boring, at least not for me. I’ve always wondered exactly how those stuffing boxes work, now I know. I can imagine that as you say – it is a delicate art, finding just enough pressure to stop the leak, but not too much to overheat the shaft or seals.
I can also see how the slightest imperfection on the surface of the shaft, or on the surface of the seal, could cause a slow leak, which might tempt the owner to tighten down on the packing nut more, to compensate for the imperfections on the shaft or seal, and then it all starts heating up … which damages the seal more … which makes it leak more … which requires more tightening …
Oh yes, now I understand how this works. 😄
I will remember to add “spare stuffing box seals and clamps, some kind of lube/grease(?), plus ultra-fine water paper to smooth the shaft”, to my list of spares.
I hope it all works out OK for you, I’m sure you’ve got this. 🙏🏻
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