How easy to replace stern gland packing?

[davethedog]

Morning,

Having the boat hauled out the water in Dec and one of the things I want to do whilst she is out is to replace the stern gland packing (it is the type without a greaser), as it seems to leak a little too much even after tightening up.

So, a few questions please:
1. How easy to do this?
2. What is the best type of packing to use, graphite?

Would consider changing to a drip-less seal but that is beyond my capability I reckon.

Regards

DTD

 

[Robert Wilson]

Morning,

Having the boat hauled out the water in Dec and one of the things I want to do whilst she is out is to replace the stern gland packing (it is the type without a greaser), as it seems to leak a little too much even after tightening up.

So, a few questions please:
1. How easy to do this?
2. What is the best type of packing to use, graphite?

Would consider changing to a drip-less seal but that is beyond my capability I reckon.

Regards

DTD

I found it much easier than I feared.
My "engineer" is so tall that he couldn't get into the engine bay so "necessity ruled".
The hardest part was undoing the nuts n bolts on the coupling which were notably rusted. Once the shaft drew clear the rest of the job was straight forward.
Compressing the bellows was a bit of a struggle as I was lying upside down in a cramped space working at arms length.
But hey, I did it :encouragement: and it works really well. No more grease stuffing

Consider doing it yourself, the satisfaction will live with you for ever! Just have something like a sheet under where you work as the wee grub screws have a mind of their own......

 

[NormanS]

Packing a gland with conventional packing is very simple, provided that you have reasonable access. The principle is very simple. Packing looks like square rope, and within the stuffing box, several "rings" of packing are fitted round the shaft, with their joins not in line. The "gland" then squeezes the rounds slightly, just enough to stop water coming in.

To repack, you must first remove the gland, and then all the rings of old packing. Fancy tools are available for this, but a long thin screwnail is ideal. Personally, I prefer graphite impregnated packing, but have also used a type with Teflon successfully.

 

[Bobc]

Ditch the whole thing and replace it with a Radice seal. No more drips...

 

[Minchsailor]

Did this last year. Much easier to get the old packing out if you can remove the prop shaft, otherwise you are picking away at the old stuff in very limited space, especially if there if very little room between the rear of the gearbox/flexible coupling and the stern gland.

Lots of good info here: https://coxengineering.sharepoint.com/Pages/Sternglands.aspx

As for material there is an argument for using the PTFE type. Graphite is the 'wrong' end of the electrolytic scale for stainless steel and can cause premature wear. Certainly my prop shaft showed considerable wear in the vicinity of the stern gland (it was packed with the graphite type) and I took the opportunity to replace it. However, others have reported that it is difficult to get a drip-less seal when using PTFE. I used PTFE and it seems to be OK. It will need nipping down a couple of times during the season while it settles down.

 

[vyv_cox]

As said, repacking a traditional packing is an ancient low-tech process that needs a bit of care but is undemanding. Ensure that your cuts are accurate and done with a sharp knife and you will not have any problems. Don't overtighten when the job is done ashore, leave everything just nipped up and tighten on the water when relaunched. I have replaced packings while still afloat, which was not difficult or frightening.

My preference is most definitely for the graphite impregnated hemp rope, as PTFE has very low thermal conductivity and can easily overheat if a little too much pressure is applied.

Where things become rather more difficult is where access is very tight and there is little space to extract the old packing, clean up the internal space, and fit new. In these circumstances you could consider fitting a PSS seal, which is not too challenging, and ask for some help from a neighbour if your confidence in doing a good job is low.

 

[KellysEye]

I used a metal skewer and bent it at the end to pull the packing out. When you put as much packing as possible tighten the gland you will then find there is room for more. I had a bowl with semi circle curve of at the top to fit under the gland then I cut a hole for a pipe and sealed it the pipe went into a container to catch the drips.

The packing is: http://www.marinesuperstore.com/pre...MIh6ahtsPW1gIVhQrTCh3RmwICEAQYASABEgKpQvD_BwE

 

[davethedog]

Thanks all and access is very good so hopefully will not be "too" difficult then...

Next issue is determining what size packing I need.

 

[Spyro]

All you need to know here.
http://www.tb-training.co.uk/10sgear.htm.
After repacking it does take a bit of time running and adjustment till it beds in and you get it just right. Too tight too hot. too slack too wet. Take some careful measurements to ensure you buy the correct size of packing.

 

[GHA]

Some more info here -

http://www.pbo.co.uk/expert-advice/expert-answers/how-to-repack-a-stern-gland-step-by-step-1031

More on youtube as well.

When I replaced one a couple years ago T Norris said they had heat problems with PTFE before so now used graphite. Galvanic corrosions seems to be pretty much unknown.

 

[JumbleDuck]

Ditch the whole thing and replace it with a Radice seal. No more drips...

Until it busts, at which point you get one very big leak until the mast head disappears.

I thought of changing my shaft seal when I had a new engine put in, but decided that I would rather stick with the devil I know. Access is appalling on my boat, and there is no possible way I could make an emergency repair to a failed seal.

 

[Bobc]

Bursts? Have you seen them?

Has anyone ever heard of one bursting?

 

[JumbleDuck]

Bursts? Have you seen them?

Has anyone ever heard of one bursting?

Yes, I have read several accounts of modern seals failing, here and in the magazines. Of course stuffing glands can fail too, but the failure mode for them tends to be be gradual.

 

[Tranona]

Yes, I have read several accounts of modern seals failing, here and in the magazines. Of course stuffing glands can fail too, but the failure mode for them tends to be be gradual.

But not Radice seals. Once you have actually seen one you will realise that bursting is not something that is likely to happen. That does not mean other types of seal Including stuffing boxes) do not fail catastrophically - either the seal itself or the hose that attaches to the stern tube.

If, however you have a stuffing box that is an integral part of the stern tube total failure is unlikely although the probability of slow leakage still exists.

 

[ghostlymoron]

I much prefer the arrangement where the stuffing box screws direct to the stern tube.
Relying on a piece of rubber hose, although high spec, seems risky to me.
Advice to OP is he will need calipers to measure the prop shaft and internal size of housing.

But not Radice seals. Once you have actually seen one you will realise that bursting is not something that is likely to happen. That does not mean other types of seal Including stuffing boxes) do not fail catastrophically - either the seal itself or the hose that attaches to the stern tube.

If, however you have a stuffing box that is an integral part of the stern tube total failure is unlikely although the probability of slow leakage still exists.

 

[Tranona]

I much prefer the arrangement where the stuffing box screws direct to the stern tube.
Relying on a piece of rubber hose, although high spec, seems risky to me.
Advice to OP is he will need calipers to measure the prop shaft and internal size of housing.

However, such things are not used these days primarily because of the move to flexibly mounted drive trains. It can be done though if you have for example an Aquadrive or use a very flexible coupling such as a Centaflex or Bullflex. I used the latter to link to a Stuart Turner stern tube with shaft bearings both end, but dispensed with the stuffing box and use a Volvo type seal. Best of all worlds.

 

[Bobc]

Volvo seal is the same as a Radice seal.

 

[Tranona]

Volvo seal is the same as a Radice seal.

Not quite - although they are both made by Radice. Their own version has a grease point and a vent or water feed which is arguably better. I have just replaced a Volvo with a Radice.

Neither is likely to burst!

 

[Bobc]

Not quite - although they are both made by Radice. Their own version has a grease point and a vent or water feed which is arguably better. I have just replaced a Volvo with a Radice.

Neither is likely to burst!

Yes I'm aware of that (as I swapped from Volvo to Radice a couple of years ago). Same basic product and princpal though.

 

[JumbleDuck]

But not Radice seals. Once you have actually seen one you will realise that bursting is not something that is likely to happen.

So what happens if that big rubber thing gets a split in it? Is there another seal? I have no doubt, by the way, that modern seals have their advantages and can work well, but I have not yet seen one I would care to have in a position (mine) where access is completely impossible.