Stern gland packing

It is not possible to just add extra rings of packing: if it seems so, something is seriously wrong with the way the gland was previously packed.

In my experience, a full renew is impossible while on the water. But you can do a partial renew provided you don't mind a fair bit of water coming in to the bilges.

Most (not all) stern gland fittings take four rings of packing. The top two can usually be picked out and replaced readily enough, but it takes nerve to do the third as by then there is usually a considerable inrush of water. Don't even think about the fourth. It helps to have the new rings ready to fit and copiously greased in advance.

The top ring should only just fit into the gland. Once it is tapped in you then screw down the clamp and tighten the greaser. Other threads have discussed how to judge the amount to screw down, but a simple approximation is, until the gland just stops dripping.

The above is not a substitute for a full change but will help if the old stuff is badly worn and leaky with the clamp fully tightened.
 
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I have totally replaced mine several times afloat. The amount of water coming into the boat was surprisingly low, mine is a 1.25 inch shaft, the clearance between shaft and gland body is only 1-2 mm. Our engine bilge is large and the pump easily coped with the flow. A rag wrapped around the gland will hold water while you prepare for your next move.

The reason I have done it several times is that initially I chose PTFE packing. Although I thought I had done it well it overheated drastically and we had to pour seawater over it constantly to get back to our berth. Thinking it was my cockup I did it again, with the same result. At this stage I replaced the PTFE with cotton and graphite, perfectly OK and still so after a couple of years.

The thermal conductivity of PTFE is very low, which I assume was the cause of the problem. It is fine for static joints but I would not use it for a dynamic one.
 
Did it recently on my MoBo, 1.5" shaft, after having quick look on coxeng website.
Many folks DO just shove another ring on top of old, which just delays the evil day.
Previous owner(s) has obviously done this on my new to me boat.

Prepared several " hooky" type tools in advance, which were useful to remove the final bits of rock hard cruddy packing, which was struggle to get out simply due to awkward access location of stern gland.
No deluge pouring in... just a slight trickling stream which curiously helped loosen and wash out last bits of old stuff.
First ring of new packing stopped in flow of water.
Now done both shafts.
Bought packing from Ebay, you can buy a metre for same price of measly few inches you get in a chandlery pre pack !.
 
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Thanks guys. This has given me confidence to give it a go. I still have about 3 threads of adjustment left, hopefully this will take me into the winter. I renewed it on the hard around three years ago and I have done thousands of hours on it. I very rarely pump grease into it, just take up the slack when the drip gets to much.
 
chrishelen said:
Thanks guys. This has given me confidence to give it a go. I still have about 3 threads of adjustment left, hopefully this will take me into the winter. I renewed it on the hard around three years ago and I have done thousands of hours on it. I very rarely pump grease into it, just take up the slack when the drip gets to much.
Click to expand...

The grease is not for the packing but to fill the tube which reduces the flow of water when the shaft is stationary The packing will of course wear doing the sort of hours that you do.
 
vyv_cox said:
I have totally replaced mine several times afloat. The amount of water coming into the boat was surprisingly low, mine is a 1.25 inch shaft, the clearance between shaft and gland body is only 1-2 mm. Our engine bilge is large and the pump easily coped with the flow. A rag wrapped around the gland will hold water while you prepare for your next move.

The reason I have done it several times is that initially I chose PTFE packing. Although I thought I had done it well it overheated drastically and we had to pour seawater over it constantly to get back to our berth. Thinking it was my cockup I did it again, with the same result. At this stage I replaced the PTFE with cotton and graphite, perfectly OK and still so after a couple of years.

The thermal conductivity of PTFE is very low, which I assume was the cause of the problem. It is fine for static joints but I would not use it for a dynamic one.
Click to expand...

I tried the Yanmar stern gland today after 8 minutes - cool enough to hold but obviously getting to hot. and then the Yanmar water alarm went off again. Nothing wrong with the seacock so I shall have to look at the impeller (and replace the packing this lay-up). The Perkins' stern gland nicely just warm but on rest had a virtual stream of drips. I wound down the greaser and the drips stopped. Need to repack that as well! (sorry OP - Vyv Cox and I had had stern gland PM exchange).
 
mjcoon said:
Gimlet-type bit in your screwdriver?

Mike.
Click to expand...
I've just done mine (out of the water). Gimlet didn't work for me, I couldn't turn it due to it's T handle getting blocked by the shaft.
What did work was a long (4 or 5 inch) X head self tapper with a sharpened point and first turn of thread. Screwed it with an electric screwdriver and it went in like going through butter.
Pulling it out with 3 turns of packing was a different story. Pulling with pliers or mole-grip didn't work, but tightening an adjustable spanner on the self tapper just below the head, finding a fulcrum and levering against the adjustable with a large screwdriver worked a treat.
 
Thanks for all replies. Mines a commercial boat so downtime is at premium. I will if need be add a few rings until annual liftout in January. Then I will tackle the beast.
 
I dont know what type of vessel you have, or the tube and shaft sizes.

It might be worth checking ASAP's Orbitrade Volvo type rubber seals. Fitted one in April this year, highly delighted.

No drips at all, bilge was perfectly dry untill a day and night of heavy rain when rainwater got in through the anchor hawse hole and down the keel stepped mast. Our anchor locker and mast both drain to the deep bilge.

I moved our seal forward 200mm using a thick wall fibreglass exhaust tube joiner to give easier access. Big improvement-I can now reach it!

A club member has had a Volvo type seal fitted to his Westerly for 16 years, still good. I expect at least 10 from ours, if not more, and it only requires a simple annual greasing, through a threaded port. It is vented to well above the waterline with a tube, so no "Burping" is needed after lifting or drying out.

Perhaps worth considering.
 
rotrax said:
I dont know what type of vessel you have, or the tube and shaft sizes.

It might be worth checking ASAP's Orbitrade Volvo type rubber seals. Fitted one in April this year, highly delighted.

No drips at all, bilge was perfectly dry untill a day and night of heavy rain when rainwater got in through the anchor hawse hole and down the keel stepped mast. Our anchor locker and mast both drain to the deep bilge.

I moved our seal forward 200mm using a thick wall fibreglass exhaust tube joiner to give easier access. Big improvement-I can now reach it!

A club member has had a Volvo type seal fitted to his Westerly for 16 years, still good. I expect at least 10 from ours, if not more, and it only requires a simple annual greasing, through a threaded port. It is vented to well above the waterline with a tube, so no "Burping" is needed after lifting or drying out.

Perhaps worth considering.
Click to expand...

Thanks. I will check it out.
 
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