Flexible stern tube gland

[fisherman]

A cautionary tale. Fv here found water ingress due to the flexible element of the internal stuffing box holder being split. A repair with rubber work gloves and jubilee clips held for not very long, the gland slipped forward, rotated with the shaft and the rubber disintegrated, they only got in due to the bilge pumps keeping pace with the inflow.
This can't be a very regular occurrence, many boats have these fitted, and I always draw attention to the fact that we are floating courtesy of the jubilee clips, but I had not come across this problem. Thinking about a work around, maybe a piece of inner tube tied back ready to pull forward over the rubber? The gland should have lugs which engage with the stern tube fitting to stop it rotating and stressing the rubber, it would need to be tied back to stop it slipping forward and rotating freely. If the stuffing box was very tight the gland would rotate within limits every ahead/astern movement.

 

[ghostlymoron]

A properly engineered stern gland has 'dogs' which engage to avoid stressing the rubber as you say and as described on Vyv Cox's website but many don't have them and rely on the strength of the rubber alone. Surprisingly, not many failures seem to be reported but I'd be concerned if mine were this design.

 

[scottie]

Quality of rubber “hose” is a major factor Portmere Rubber do the correct stuff do not economise with anything else

 

[fisherman]

This is the next issue, I think a repair is being done with a.n. other piece of hose. In extremis I suppose you could stuff some greased cotton material in and lash the outer gland on top.

 

[fisherman]

The engineer in charge has fitted a piece of spiral wound wire reinforced oil proof tube. He says the stern tube should be full of grease and that would keep out the water, and a simple repair could be effected with flat oilskin material and clips. Hmmm.

 

[ghostlymoron]

That's completely wrong, the stern tube must be able to convey water to the stern gland to cool it. Packing it with grease would cause it to overheat.

The engineer in charge has fitted a piece of spiral wound wire reinforced oil proof tube. He says the stern tube should be full of grease and that would keep out the water, and a simple repair could be effected with flat oilskin material and clips. Hmmm.

 

[rotrax]

That's completely wrong, the stern tube must be able to convey water to the stern gland to cool it. Packing it with grease would cause it to overheat.

There are different types of stern glands.

My NZ boat has a Bukh engine in it with the Bukh stern gland. This is oil fed through a screw down greaser with heavy oil. Forget to screw it down and it leaks. Oiled correctly it is as dry as a nuns crutch.

Many canal narrowboats-almost all in fact-have a remote greaser and it is normal to screw it down every morning before starting the engine untill it goes stiffer, telling you the grease has filled the space.

So, not ALL stern glands use water as a lubricant/coolant.

Some use grease or heavy oil.

 

[PuffTheMagicDragon]

I had a similar case when the old hose started swelling (because of grease) and water started to leak through the delaminated rubber. I had a length of suitable hose but, of course, couldn't replace it while afloat. The solution was to slit a suitable length and refasten it over the rotten hose... using several hose clips. That cured the leak and a proper replacement was installed once we were in port and on the hard.

 

[NorthUp]

The engineer in charge has fitted a piece of spiral wound wire reinforced oil proof tube. He says the stern tube should be full of grease and that would keep out the water, and a simple repair could be effected with flat oilskin material and clips. Hmmm.

My advice would be to find another engineer.

 

[ghostlymoron]

My advice would be to find another engineer.

Me too. Any stern tube that has a cutless bearing requires cooling water and most boats post 1980 are so equipped. Possibly earlier as well - grease is a poor conductor of heat.

 

[Poignard]

That's completely wrong, the stern tube must be able to convey water to the stern gland to cool it. Packing it with grease would cause it to overheat.

I agree, and have confirmed that by experment on my own boat.

 

[rotrax]

I agree, and have confirmed that by experment on my own boat.

See post #7.

Google 'Bukh oil stern gland'

Look at remote greasers fitted to THOUSANDS of narrowboat stern glands.

Your experience is obviously not all-encompassing..................................

In my experience the most likely cause of overheating of a traditional stern gland is overtightened packing. Seen a narrowboat shaft glowing red because of that!

 

[fisherman]

Me too. Any stern tube that has a cutless bearing requires cooling water and most boats post 1980 are so equipped. Possibly earlier as well - grease is a poor conductor of heat.

Yes, water to the cutless, but the inboard gland is often just packing and grease. I once had a boat with greased bearings in and out, and have seen many with a lubricant delivery tube outside the hull.
Tightening the packing may result in the inner gland rotating up to the engagement of the dogs, thus straining the rubber.

 

[Poignard]

Your experience is obviously not all-encompassing..................................

Did I claim that it was all-encompassing?

On my boat, which has a traditional packed gland, if I force a lot of grease into the stern tube, the gland gets hot. If I apply only a little, it does not.

Therefore, I feel justified in agreeing with GhostlyMoron (see Post #6).

 

[rotrax]

Did I claim that it was all-encompassing?

On my boat, which has a traditional packed gland, if I force a lot of grease into the stern tube, the gland gets hot. If I apply only a little, it does not.

Therefore, I feel justified in agreeing with GhostlyMoron (see Post #6).

But GhostlyMoron stated that grease in a stern gland is wrong.

Clearly, it is obviously is a neccessary component in some.

As you have found, too much is likely to cause overheating.

Horses for courses-maintain a grease type correctly, no problem.

Forget the grease, there might well be one.

I have two high quality USA made bronze traditional stern glands-no greaser on either- on the shelf at home. I changed both boats to Volvo type seals. Water is a vital lube/coolant with the Volvo seals.

You must ask yourself if water was the only coolant/lubericant required, why are many stern glands made to take grease?

Extra complication to what end?

Please advise-I would really like to know the answer.

 

[Poignard]

But GhostlyMoron stated that grease in a stern gland is wrong.

Clearly, it is obviously is a neccessary component in some.

As you have found, too much is likely to cause overheating.

Horses for courses-maintain a grease type correctly, no problem.

Forget the grease, there might well be one.

I have two high quality USA made bronze traditional stern glands-no greaser on either- on the shelf at home. I changed both boats to Volvo type seals. Water is a vital lube/coolant with the Volvo seals.

You must ask yourself if water was the only coolant/lubericant required, why are many stern glands made to take grease?

Extra complication to what end?

Please advise-I would really like to know the answer.

As I see it, the grease lubricates the white-metalled bearing supporting the forward end of the shaft. It doesn't need much grease to do that and introducing more grease than is necessary for that purpose does nothing except displace the water from the sterntube. Not only is this a pointless waste of grease, and a source of marine pollution, but the water that would have had some cooling effect on the bearing due to its proximity to it, is gone, and the bearing runs hotter than it otherwise would.

 

[fisherman]

Yerbut, if you only have a stuffing box there is no white metal bearing....

 

[rotrax]

As I see it, the grease lubricates the white-metalled bearing supporting the forward end of the shaft. It doesn't need much grease to do that and introducing more grease than is necessary for that purpose does nothing except displace the water from the sterntube. Not only is this a pointless waste of grease, and a source of marine pollution, but the water that would have had some cooling effect on the bearing due to its proximity to it, is gone, and the bearing runs hotter than it otherwise would.

So, as I asked, why would they make a stern tube with a bearing and provide a greaser if water would do the job?

It is only a pointless waste of grease and a scource of pollution if the greasing is overdone.

On tubes/glands of that type, grease is intended to be there by the designer.

Just dont overdo it.

 

[Poignard]

So, as I asked, why would they make a stern tube with a bearing and provide a greaser if water would do the job?

It is only a pointless waste of grease and a scource of pollution if the greasing is overdone.

On tubes/glands of that type, grease is intended to be there by the designer.

Just dont overdo it.

I think we have been in agreement, more or less, without realising it!

I apply hardly any grease to my bearing, a fraction of a turn of the greaser every now and then.

 

[vyv_cox]

The usual advice is that there should be minimal drips from a packed gland when the shaft is turning, maybe 1-2 drops per minute. If it still drips when rotation stops adding a little grease will arrest it as the grease floats on the water in the stern tube and blocks the leakage.