Stern gland packing two rings?

J

jasavo

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Wow, life is different now I have my first boat. Before, I just sailed on other boats and their owners took care of all the maintenance; sailing was cheap and stress free.

However I now have the stern gland apart and pulled out two packing rings. I always thought there should be at least three? For my peace of mind, was the stern gland correctly packed by the previous owner with two rings? Or was it incorrect and I should be looking to put back three rings on re-assembly?

All comments welcome.



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I think you are correct. A marine engineer told me that there were always an odd number and that 7 was the most common on larger boats. I cannot offer an explanation for this, but I would repack with 3 if you can if only to appease the gods of marine engineers.

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as an apprentice fitter, more years ago than i can remember, i learned to repack stuffing boxes, glands whatever you want to call them. the first thing i learned was that every time i thought that i had got al the old rings out, there was still one in. if you havent got a flexible packing ring hook you will have a heck of a job getting them all out. when you can feel a metallic feel to the hook when you stab it into the stuffing box you have won. there are no hard and fast rules about odds and evens, it is all about how many the designer of the box thought would do the job. i think that 2 is not enough and if you havent got all the old ones out you are wasting your time.
check again
stu

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I'm not sure there are any rules . . . there were three rings in mine, but they seemed to be a slightly odd size. 6mm proved too big, got three in but the shaft would barely turn, so got 5mm and found I had to put 4 in to allow plenty of future room for further screwing up should it be necessary.

The main thing is to make sure the joins in the rings are staggered. Screw up hand tight, then see what happens. A drip every few minutes is considered ideal by most people - the important thing is that it doesn't run hot and wear the prop shaft.

I'd never done it before and everyone told me my boat had a lip seal type shaft - took a while to figure out what was going on. I too used to sail OPs all the time, but now I have my own boat it's so much better - it's a steep learning curve but worth it once you know your own boat inside out.

- Nick

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Right!

Confirm - there is always one jammed really tight down the bottom. Its the one the previous owner didn't change either.

Most have 3 rings but I've occasionally seen one with 4. Its getting harder to find Imperial sized packing now for older boats, metric fits but isn't ideal.
 
Re: Really need to remove it all?

Is it so necessary to remove all the packing?
And how often should it be repacked?
I know of people who add just an extra ring if needed.
I've even heard of people who repack in the water, leaving the last ring or so in to prevent a catastrophe.
Mine still doesn't leak after 18 months ashore, I was going to repack but it all seems OK. I guess if it starts to drip too much at some point then I will re-pack it.

As regards heat, how hot is too hot? Mine doesn't seem to get very warm, even after lengthy running.

<hr width=100% size=1>I've got wind......................
...............................in my sails!
 
Re: Really need to remove it all?

It certainly isn't necessary to repack every year. The rings are thick with grease for lubrication, and because it might just affect the shaft if that fails, even with the addition of grease through a greaser, I repack as a matter of course every three years to err on the side of caution. This is with a low-revving engine on a sailing yacht, used for maybe 100 hours per annum, using a normal, low-pressure gland. For the same reason I always do all rings together. Of course, it will be necessary to repack if the seal starts to leak in use, but judicious tightening of the gland will control leaks for a while, or, as you suggest, just changing a couple of the rings.

If the gland seems to have developed a tendancy to leak, even with regular changes, then suspect (i) engine misalignment; (ii) bent shaft; (iii) worn shaft; (iv) worn cutlass bearing (v) wrong sized packing.

The gland is also partly water lubricated from the outside, which is why there normally is a very slow drip when in use. It MUST NOT be hot to the touch in use, if so it is packed too tight. Just warm, specially as new packing is wearing in, is normal, but there can be no perceptible heat.

With practice, changing the rings while afloat is not difficult. It depends on how far below the water-line the stuffing box is situated, and how close a fit the cutlass bearing provides, as to how fast it will leak with the stuffing removed. Mine is a steady flow, but in previous threads people have said they get no more than a few drops.

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Number of turns depends on the pressure the gland had to seal against. You can imagine the numbers on boiler feed water pumps operating at 800/900psi -these had two lots of turns separated by solid brass ring into which cooling water was pumped. Superheated were also a joy - it was normal practice to repack with just the valve separating your fingers from the upstream pressure - I must confess I never did all the turns on these jobs.
Depends on your exprience and confidence as to doing small boat valves and glands in the water, the pressure is minimal. The gland if repacked properly should last years. never run it hot and leave a drip per minute. If I was going around the world I would have packing stern glands every time, if push comes to shove I have used unraveled woolly jumpers when there was nothing left in the stores.

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Re: Really need to remove it all?

I'll test how warm mine gets next time, it hardly drips at all - it's all at arm's length through the cockpit sole though! Probably why it's not one of my favorite jobs!



<hr width=100% size=1>I've got wind......................
...............................in my sails!
 
Mine has only two rings (yes, I did check for a third!) . The packing should last at least 5 years as long as it is greased and checked for correct adjustment regularly.

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Re: Right!

AndrewB,
I agree most chandlers seems to sell metric and quote it's an imperial equivalent - which often it is not, I gave up with the advice from UK suppliers and chandlers and bought over the internet from the states where imperial is still well understood.
I also managed to find a gortex type that does cause corrosion of the s/s shaft and doesn't require any grease. And it work too!

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Re: Right!

of course this should have read doesn't!!:-

I also managed to find a gortex type that doesn't cause corrosion of the s/s shaft and doesn't require any grease. And it work too!

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