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Putting Stern Gland Packing on Top of Old


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#1 Serendipity

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Posted 02 January 2010 - 01:34 PM

Got a lot of water coming through my 'maintenance free' stern gland which is now adjusted up as far as it will go. It's almost a steady trickle when the prop shaft rotates, although it settles to a drip every couple of seconds after it's been stationary a while.

I'm very tempted to back of the adjuster nut and put some new packing in whilst it's in the water, if only as a temporary measure.

I understand it's generally considered a no no to leave the old packing in - can anyone tell me why please?
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#2 steelaway

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Posted 02 January 2010 - 02:20 PM

Got a lot of water coming through my 'maintenance free' stern gland which is now adjusted up as far as it will go. It's almost a steady trickle when the prop shaft rotates, although it settles to a drip every couple of seconds after it's been stationary a while.

I'm very tempted to back of the adjuster nut and put some new packing in whilst it's in the water, if only as a temporary measure.

I understand it's generally considered a no no to leave the old packing in - can anyone tell me why please?



Hi

I am a bit confused by the 'maintenence free' Do you mean the standard stuffing gland that you grease daily, or something else?
Stuffing glands need repacking every few years. Its not hard to remove the old packing and fitting a completly new set.
I cut seperate rings and push them individually (possibly 3 off), making sure the cut ends are not in line.
You shouldn't have much water leakage through the prop whilst you are repacking.

Alex
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#3 Serendipity

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Posted 02 January 2010 - 02:26 PM

Hi

I am a bit confused by the 'maintenence free' Do you mean the standard stuffing gland that you grease daily, or something else?

Alex


Hi Alex,

It's a conventional stuffing gland on a rubber stern tube extension, but no greaser.

Edited to say: Like the second diagram here.

I'm miles from anywhere and don't fancy removing the old stuffing whilst in the water.

Julian

Edited by Serendipity, 02 January 2010 - 02:32 PM.

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#4 Tony Brooks

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Posted 02 January 2010 - 03:09 PM

Hi Alex,

It's a conventional stuffing gland on a rubber stern tube extension, but no greaser.

Edited to say: Like the second diagram here.

I'm miles from anywhere and don't fancy removing the old stuffing whilst in the water.

Julian


In the situation you describe then by all means just put more packing on top of the old BUT:-

The old packing will have lost its properties and become hard, especially as there is no greaser!. This will tend to wear the shaft and the hard packing may not seal as well as the new, softer stuff. It might also wear away faster, necessitating more frequent adjustment.

Good practise is to hook the old stuff out and replace all the packing but in an emergency putting new on top of old will suffice until you can get somewhere you can do the job properly.


Please do not refer to this as a maintenance free gland. That name is reserved for glands that have no packing and, in theory, require no adjustment and no or very little maintenance. Yours is a packed gland without greaser.

I hope this is on a river boat because I do not fancy lubricating a rubber bearing with the mud slurry we have in canals, however another member swears Cutless bearings are fine on canals. I have my doubts.
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#5 Laurie.Booth

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Posted 02 January 2010 - 03:21 PM

Sorry to be very ignorent about stern tube packing.
Can the stern tube be repacked while the boat is in the water?
I always thought water would rush in (enough to sink the boat) so I have always had it done by a "professional" please forgive me for asking this.
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#6 DHutch

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Posted 02 January 2010 - 03:30 PM

You can repack a conventional stern tube gland with the boat in the water.
- If the gland is worn it may come in fairly fast (be set up with a good bildge pump to lift it out again as you work) but if its good shape and you put a few turns on the greaser you actually get very little in to the boat. Certainly backing the collar off and putting another turn in wont really let any typical because although your taking the preload off it the packing doest really move.

Quite how the related to the op without an greaser i dont know, and the cutlass bearings do not hold water back like the conventional bronze ones but i have to admit i would be happy to have a go at putting another turn of packing in if it where my boat. As i say, make sure you have a decent bilge pump and if possible have two of you there incase it all gets a bit exciting. But even if it get really bad a good piece of oily rag bound on with string will keep a boat floating for as long as the bilge pump runs. Days if its a good piece of rang, months or years if you can charge the battery.


As you can see from the image here (drawn the other way round to most, prop is on the right hand end!) after the stuffing box you have the actual sterntube bearing which is a long plain bearing which when greased should be near on waterproof when the shaft isnt turning.
Posted Image


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#7 ditchcrawler

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Posted 02 January 2010 - 03:35 PM

Removed as I was talking out of the back of my head

Edited by ditchcrawler, 02 January 2010 - 04:12 PM.

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#8 Laurie.Booth

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Posted 02 January 2010 - 03:45 PM

Hi Daniel,
Thanks for the information, I'll certainly look into doing this myself.
Clarrie my boat is in dry dock this Easter so I can practice in the dry.
Thanks again
:lol:
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#9 Kraken

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Posted 02 January 2010 - 03:47 PM

The one shown here has no adjustment or packing and requires very little maintenance until it fails. So if yours is like that you can't repack it and I am not sure what you have adjusted.



Look at the second one
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#10 Tony Brooks

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Posted 02 January 2010 - 04:26 PM

Sorry to be very ignorent about stern tube packing.
Can the stern tube be repacked while the boat is in the water?
I always thought water would rush in (enough to sink the boat) so I have always had it done by a "professional" please forgive me for asking this.


Well, if the diagram is typical of your boat then you probably would get more water coming in than you would on a metal bearing boat with a well turned greaser, but I thought nothing of packing the hire fleet cruisers when they were afloat. In fact there is a land just behind the packing that is normally a slight clearance fit around the shaft that will stop most of the water.

Now if this is a narrowboat and you are really worried then try wrapping some mastic bandage, cling-film or similar tight around the shaft and the part of the rear bearing that protrudes form the hull. That should make it close to water tight. For goodness sake remove it before starting off :lol:

Just cut the rings before you stats dismantling the gland.
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#11 andywatson

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Posted 02 January 2010 - 04:36 PM

Sorry to be very ignorent about stern tube packing.
Can the stern tube be repacked while the boat is in the water?
I always thought water would rush in (enough to sink the boat) so I have always had it done by a "professional" please forgive me for asking this.


As per Dhutch's post below, yes, you can do it yourself and it is fairly easy.
Just have everything you need lined up and ready to go.

I pre-cut my (3 wraps) of packing before taking out the old to minimise the time with no packing in place - - although almost no water came in.
If you are worried about this why not access the outside through your weed hatch and tie a greasy rag/plastic bag around the shaft.
Copiously grease the new packing as you fit it. The new stuff does seem quite stiff.

I found my new packing took a few hours to settle down. It seemed to be too tight (with a warmer gland) or too loose (dripping too much) then all of a sudden seemed OK.

I have considered leaving 1 wrap of the old stuff in place as even with 3 new wraps of packing the adjuster is swallowed a long way..............?
Can Tony or another expert comment.
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#12 steelaway

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Posted 02 January 2010 - 04:40 PM

Hi

As Tony says you should be able to make tempory seal over the shaft and bearing through the weed hatch.
Plastic sheet and tywraps? But take the gland nut of slowly and check the amount of water leaking through is controllable.
I would have liked to have a grease nipple some where, just to lubricate the packing occasionally.
Check the shaft for wear when you replace the packing.

Alex
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#13 Timleech

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Posted 02 January 2010 - 04:47 PM

I have considered leaving 1 wrap of the old stuff in place as even with 3 new wraps of packing the adjuster is swallowed a long way..............?


A lot of the modern nb sterngear only takes about 3 rings of packing, in that situation I'd be inclined to replace the lot if it's giving problems. If you need more packing just because you've run out of adjustment and not because of leakage problems, I'd be tempted just to add another ring.
In your case which apparently has more than the modern average, I'd decide based on the condition of the stuff that was coming out.
A lot of old working boats had a dozen or more rings of 5/8" square packing, you wouldn't pull out all of that and replace it unless it was absolutely necessary!

Re cutless bearings on canal boats, yes they do seem to have a reasonable life in practice. It would be interesting (marginally!) to do a scientific test, maybe 2 or 3 boats in a hire fleet with cutless bearings and the rest with metallic bearings, see which lasts better. A lot of metallic bearings have their life reduced by bad engine alignment, cutless bearings should be a bit more forgiving on that front.

Tim
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#14 Serendipity

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Posted 02 January 2010 - 04:49 PM

In the situation you describe then by all means just put more packing on top of the old BUT:-

The old packing will have lost its properties and become hard, especially as there is no greaser!. This will tend to wear the shaft and the hard packing may not seal as well as the new, softer stuff. It might also wear away faster, necessitating more frequent adjustment.

Good practise is to hook the old stuff out and replace all the packing but in an emergency putting new on top of old will suffice until you can get somewhere you can do the job properly.


Please do not refer to this as a maintenance free gland. That name is reserved for glands that have no packing and, in theory, require no adjustment and no or very little maintenance. Yours is a packed gland without greaser.

I hope this is on a river boat because I do not fancy lubricating a rubber bearing with the mud slurry we have in canals, however another member swears Cutless bearings are fine on canals. I have my doubts.



Thanks for the advice Tony - I stand corrected on the 'maintenance free' bit :lol:

It's not a river boat, but a 91 NB - just because it has a flexible rubber stern tube, would it also have a rubber bearing then?

(Edited to say: Just Googled cutless bearing and see it's a rubber bearing! Although the diagram I linked to states cutless bearing, but I have no idea if I have one. All I know is that the flexible coupling and stuffing box shown are identical to my setup - but I suppose since it's designed to flex, it follows that I must also have a rubber cutless bearing at t'other end).

Your remark regarding wearing the shaft is of particular concern. Moving my problem forward, the rubber tube is showing signs of age and clearly needs replacing. I've already sourced it and just need to arrange a yard to do it. Now I'd assume there would be some wear on the shaft in any case? Would I be right to assume in that case it's important the stuffing box goes back on the shaft EXACTLY where it came off? So it's vital that the replacement tube is cut to the correct length so as to allow precise positioning of the stuffing box back on the shaft before tightening the jubilee clips? If my assumptions are correct, it sounds like a big ask to me, and maybe i'd be better off replacing the lot with something more traditional.

As someone whose never seen the innards I'd appreciate your comment.

Julian

Edited by Serendipity, 02 January 2010 - 05:04 PM.

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#15 andywatson

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Posted 02 January 2010 - 05:06 PM

A lot of the modern nb sterngear only takes about 3 rings of packing, in that situation I'd be inclined to replace the lot if it's giving problems. If you need more packing just because you've run out of adjustment and not because of leakage problems, I'd be tempted just to add another ring.
In your case which apparently has more than the modern average, I'd decide based on the condition of the stuff that was coming out.
A lot of old working boats had a dozen or more rings of 5/8" square packing, you wouldn't pull out all of that and replace it unless it was absolutely necessary!
Tim


Thanks for that.
I replaced my stern gland packing for the first (and so far only) time soon after I got the boat about 4 years ago. Based on your comments I think mine must be designed to take more than 3 wraps.
(EDIT TO ADD ie like the one on DHutch's diagram)
It doesn't leak much.

Edited by andywatson, 02 January 2010 - 05:20 PM.

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#16 Tony Brooks

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Posted 02 January 2010 - 05:45 PM

As per Dhutch's post below, yes, you can do it yourself and it is fairly easy.
Just have everything you need lined up and ready to go.

I pre-cut my (3 wraps) of packing before taking out the old to minimise the time with no packing in place - - although almost no water came in.
If you are worried about this why not access the outside through your weed hatch and tie a greasy rag/plastic bag around the shaft.
Copiously grease the new packing as you fit it. The new stuff does seem quite stiff.

I found my new packing took a few hours to settle down. It seemed to be too tight (with a warmer gland) or too loose (dripping too much) then all of a sudden seemed OK.

I have considered leaving 1 wrap of the old stuff in place as even with 3 new wraps of packing the adjuster is swallowed a long way..............?
Can Tony or another expert comment.




Not expert please.

I would never leave any old packing in place except in an emergence because of the reasons given in an earlier post.

I think the "three rings" thing has come about from the "packing inside the nut" type glands often found on cruisers and does not hold good for typical narrowboat glands or come to that many Broads hire cruisers. Keep adding rings and pushing firmly home until he last ring is just BELOW the top of the "hole". Overfill it or fill it level and you may never get the "pusher" back into the hole because you can not line it up. This begs the question of how much packing to buy but I always tell my classes two metres or two pre-packs. As long as any surplus is stored in a twisted plastic bag it will keep for years.
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#17 nb Innisfree

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Posted 02 January 2010 - 05:57 PM

When I fitted our packing I inserted two rings first and then pushed them home with the 'pusher', removed pusher then did the last one. I put loads on of pressure to make sure it was all bedded in then backed pusher off until loose turned shaft several tims to loosen packing and then adjusted. I later fitted a Python Drive and have not needed to adjust for a couple of years and there is no water drips at all, tho I do use a lot of grease.
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#18 Tony Brooks

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Posted 02 January 2010 - 06:01 PM

Thanks for the advice Tony - I stand corrected on the 'maintenance free' bit :lol:

It's not a river boat, but a 91 NB - just because it has a flexible rubber stern tube, would it also have a rubber bearing then?

(Edited to say: Just Googled cutless bearing and see it's a rubber bearing! Although the diagram I linked to states cutless bearing, but I have no idea if I have one. All I know is that the flexible coupling and stuffing box shown are identical to my setup - but I suppose since it's designed to flex, it follows that I must also have a rubber cutless bearing at t'other end).

Your remark regarding wearing the shaft is of particular concern. Moving my problem forward, the rubber tube is showing signs of age and clearly needs replacing. I've already sourced it and just need to arrange a yard to do it. Now I'd assume there would be some wear on the shaft in any case? Would I be right to assume in that case it's important the stuffing box goes back on the shaft EXACTLY where it came off? So it's vital that the replacement tube is cut to the correct length so as to allow precise positioning of the stuffing box back on the shaft before tightening the jubilee clips? If my assumptions are correct, it sounds like a big ask to me, and maybe i'd be better off replacing the lot with something more traditional.

As someone whose never seen the innards I'd appreciate your comment.

Julian


I am baffled by the way the inland part of the industry keeps on producing no-standard designs so I have no way of knowing if you have a rubber bearing or not. I hope that you have because without an "oily" lubricant I would hate to see what a plain bearing without grease has done to the shaft or the shaft to the bearing.

I would expect the yard to slip/dock/lift the boat to replace that rubber hose because if it is a rubber bearing once the gland is off you will get a good inrush of water. If they do take the opportunity to have a look at the rear bearing from outside the boat. Also give the prop a good heavy lift and drop it. It should move vertically or horizontally a tiny amount as the rubber in the bearing compresses but there should be no clonk or free movement indicating bearing wear.

As long as you have a stainless steel shaft I would not expect the wear to be significant, in fact not much more than polishing. However no-one will know until the gland is off. Unless the shaft is so badly worn that replacement is advised I would not worry too much about getting the gland exactly in the same place. Normally there are so many turns of packing that it makes little difference to getting a seal.

The most important thing about the hose length is that the back of the gland assembly and the front to the stern tube assembly should be equipped with interlocking castleations forming a dog clutch. They are there so that if the gland is overtightened the twist imparted to the gland assembly is taken by the castleations and not the hose. Fitting an overlong hose could allow the gland to twist the hose apart.

You may have a nylon, Paxalon or other form of self lubricating rear bearing. Hopefully the yard that does the job will be able to tell you what you have there.
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#19 Serendipity

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Posted 02 January 2010 - 06:15 PM

The most important thing about the hose length is that the back of the gland assembly and the front to the stern tube assembly should be equipped with interlocking castleations forming a dog clutch. They are there so that if the gland is overtightened the twist imparted to the gland assembly is taken by the castleations and not the hose. Fitting an overlong hose could allow the gland to twist the hose apart.


It doesn't, and there are indeed signs of twisting on the hose. However the new hose I have sourced is a triple laminated re-inforced affair specifically sold for the job (no idea about the one on there), and is thicker than the old one (about 10 mm as oppsed to old which is about 7-8mm), and is only about 60 mm between the jubilee clips so i would hope more rigid than the old.
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#20 Timleech

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Posted 02 January 2010 - 06:29 PM

I think the "three rings" thing has come about from the "packing inside the nut" type glands often found on cruisers and does not hold good for typical narrowboat glands or come to that many Broads hire cruisers.


I've just braved the cold to check in my 'used parts bin', there are two conventional (edit) stuffing boxes for 1.5" shafts, evidently from two different sources as there are slight differences, each has a recess for the 8mm packing which is 31mm deep - in other words, will only take three rings. Yes you will be able to get a fourth in when the gland has been nipped up a few times, but not with new packing. These are absolutely typical in today's narrowboats, and are the same as sold by the (national) chandlers down the road.

Tim

Edited by Timleech, 02 January 2010 - 06:41 PM.

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