Deep sea seal versus traditional packing box and greaser

[Tranona]

There is a danger of using a term such as "modern" without understanding the differences in designs.

If posters (alahol2 and fergie_mac66 for example), have any real evidence that boats fitted with lip seals design shaft seals have sunk because of failure of the lip seals, please share it with us.

Otherwise such statements can be filed in the "urban myth" department! and ignored.

 

[Mrnotming]

lip seals different to face plate seals

Tranona corrects me correctly.

lip seals should continue to seal if engine is displaced somewhat. Face plates seals depend upon pressure being maintained of one face upon the other.Perhaps they are no longer used, and just as well if not!Good sailing n boating to all!

 

[alan_d]

I do it, burping the volvo gland that is, but is it necessary, boat is on a drying mooring and I have to empty the cockpit locker and climb in to burp it on the Westerly Konsort.

Wouldn't you be quicker removing the panel at the side of the quarter-berth? Or perhaps your cockpit locker is not as full as mine.

 

[tabernacleman]

Mm! no panel at the side of the quarter berth, and yes, the locker is pretty full, What year your Konsort,

 

[Pye_End]

There have been three near sinkings in our club over the last few years from modern shaft seals. Why on earth would anyone risk it for the sake of a few drips in the bilge?

Please give more details.

Do you know what sort of seals they were; how old they were/what state they were in; why they failed; why were they 'near sinkings' and not 'sinkings'; what is a 'near sinking exactly?

Ditto fergi mac66.

I suffered a 'near sinking' a few weeks ago and suspected the shaft seal. By this I mean returning to the boat after a few days and finding sea water just above the floor boards. In the end it turned out to be the blanking plug for the log hadn't quite sealed - probably a bit of weed or grit.

I have not heard first hand of a sinking due to the stern gland, but have come across several skin fitting failures (although I know of the reputation for the Deep Sea Seal). Which is more risky (statistically)?

If people have first hand hard information on stern gland failure please supply the detail as without it we are still left wondering.

 

[tabernacleman]

Pedantic tendencies

can't help wondering if near sinking - sinking - floating is on a par with not quite sealed - sealed - not sealed ; or am I being nearly pedantic

 

[doug748]

But non by by traditional glands !

The old style stuffing box itself can fail, but it is probably rare. It still sinks boats though.
What does fail is the rubber sleeve or bellows, which either leaks through wear, neglect or being ripped off the stern tube.
All stern gear arrangements are to some extent suspect.
The journalist and sailor Nigel Calder wrote, Speaking of modern stern glands, (I paraphrase, as my copy of YM is on the boat):
"I have never heard of one failing"
"My favourite is the PSS seal"

 

[alahol2]

I don't know the makes involved but two of the 'near sinkings' were caused by the seal 'siezing' to it's mating face during winter storage. The boats were launched, the engine started and the rubber bellows(?) was torn. The other one I know of required an ILB callout, this was caused by a bit of 'twig' getting caught between the faces of the seal.
Near sinkings is perhaps a bit strong, but if I were on one of those boats I would have felt like the boat was in imminent danger.
I realise that the first two cases are user error/lack of knowledge but I still can't understand why anyone would risk changing to one of these seals if they have a perfectly good stuffing box.

 

[Tranona]

I don't know the makes involved but two of the 'near sinkings' were caused by the seal 'siezing' to it's mating face during winter storage. The boats were launched, the engine started and the rubber bellows(?) was torn. The other one I know of required an ILB callout, this was caused by a bit of 'twig' getting caught between the faces of the seal.
Near sinkings is perhaps a bit strong, but if I were on one of those boats I would have felt like the boat was in imminent danger.
I realise that the first two cases are user error/lack of knowledge but I still can't understand why anyone would risk changing to one of these seals if they have a perfectly good stuffing box.

This shows how important it is not to use the term "modern" as a catchall for all non stuffing box seals.

What you are describing here is failure of FACE seals in the way that critics suggest they fail. Perhaps this is why one of the main designs (Deep Sea Seals) has an "emergency" seal with a bright red tag on it incorporated in the stationary part. A modification to the original design. I wonder why?

Would you fit a shaft seal to your boat that required a manually actuated emergency seal if it failed?

 

[blackfish]

My Manecraft Deep Sea Seal failed catastrophically last year. Water half-way up the engine. Just managed to stem the flow with two bilge pumps flat out. Replaced with a traditional stuffing box over the winter (from T Norris Marine) and no problems this year. Also had stuffing box on previous boat which was virtually maintenance-free for the ten years we owned her. No contest as far as I'm concerned.

 

[Refueler]

Worried now, there are posts suggesting that peoples' packing glands don't leak much. The old boy that taught me the basics 20 years or so ago told me the worse thing was to over-tighten them, you want to see a drip every couple of minutes with engine at rest I was told. I have dutifully set them that way ever since. I am also sure I read the same advice in the instructions of one I installed not so long ago. Wrong?

Yes when you service and set-up .... then you pump in a bit of grease to stop the drip.

When you run engine and shaft does it's job ... when you stop - there'll be your drip again. If it's first run after service you may find drip is more quick - then you nip up the gland a touch till you get your drip a minute or so. Again pump in a bit of grease and drip stops till shaft turns again.

 

[jfkal]

Refurbishing one?

Sounds like you have some good experience in this. Any thoughts on whether it would be possible to change the lip seals on an old Halyard oil based stern gland?

 

[jfkal]

Sinking? You gotta be kidding

Good advice from many.Main thing touched upon is that engines move about on rubber mounts..Having fouled a rope on a previous vessel, the gap between the p Bracket and the prop was forced back about 3" by the coil of rope and the engine torn from it's mountings.There was no ingress of water as the traditional stuffing box was in use.
A lip seal would have turned this into a sinking.

Another time off Bardsey Island Wales, the boat fell off a wave so hard that the engine moved off its mounts sideways, still attached by two mounts.Later it was possible to move the engine back.
Due to the stuffing box remaining in place no water entered the vessel.

LESSON LEARNED:
A boat should be engineered differently to a washing machine, to cope with incidents which occur sometimes in the middle of the night!
If you have one of these lip seals,it may help to fit a rope cutter of proven performance.
good sailing n boating to all!

The only way I can see it sinking is unattended at the mooring. Any water squeezing through the gap between shaft and stern tube can be stopped with a wet handkerchief and the rest mopped up with a baby diaper.
Still, I see the plus points of a stuffing box here.......

 

[jfkal]

Bravo

Not wishing to be too pedantic, but as it is critical to the discussion over designs.

A Deep Sea seal and a PSS are FACE seals.

Volvo, Tides (sure seal) and Vetus are lip seals around the shaft in the same way as a stuffing box. The Halyard seal using oil as a lubricant and lip seals to keep the oil in and water out.

That clears the smoke from the facts. Thanks for that. Need to add that for that reason the Halyard does not face the problems of all the others. Worst case being some oil in the bilge or some oil in the water (not good, I admit).

 

[john_morris_uk]

Golly there's a lot of hot air generated about shaft seals.

Without any justification or argument and with the statistical nonsense of a sample of one, I will reveal that we have a PSS seal and a Halyard Aquadrive and I wouldn't change a thing.

In fact the statistical sample doubles if I recall that I fitted a PSS shaft seal to our last boat and I wouldn't have changed that either.

And just to muck the lives up of those who extoll traditional stern glands, the only time I have a serious flood in a boat was with a traditional type stern gland.

 

[Poignard]

..... , the only time I have a serious flood in a boat was with a traditional type stern gland.

In what way did the stern gland fail?

 

[Tranona]

Golly there's a lot of hot air generated about shaft seals.

Without any justification or argument and with the statistical nonsense of a sample of one, I will reveal that we have a PSS seal and a Halyard Aquadrive and I wouldn't change a thing.

In fact the statistical sample doubles if I recall that I fitted a PSS shaft seal to our last boat and I wouldn't have changed that either.

And just to muck the lives up of those who extoll traditional stern glands, the only time I have a serious flood in a boat was with a traditional type stern gland.

Without wishing to fan the flames any more, the PSS is the only face type seal that has stayed the course. It is well engineeered to overcome the fundamental weakness of face seals in this application. Earlier designs failed far more often, which is why they are no longer made. One of the weaknesses of face seals is that they rely on pressure of the bellows to creat the seal, and as you know PSS emphasise the importance of setting them up correctly. Earlier designs had less robust bellows and could open up, for example if the engine is on very soft mounts and shifted quickly from reverse to forward, or as in one case I know of when the boat was surfing and water pressure opened up the faces. Your installation with an Aquadrive does not allow any movement of the shaft so the bellows pressure never changes. Therefore, unless the bellows slips on the shaft, the faces are always in contact at the correct pressure.

Personally I believe a seal around the shaft such as lip seals or traditional packing is much more secure as any failure is due to gradual deterioration of the seal medium leading to warning leaks. Lip seals are now dominant in the (declining) yacht shaft drive market and gaining ground in power boats. I know of no mainstream builder that uses face seals.

 

[Bilgediver]

Something seriously wrong if the shaft is wearing. How can a rubber seal wear a stainless steel shaft? Can understand the seal progressively failing and leaking if it is not regularly lubricated, but if the water lubricated part of the seal is wearing you would not be able to stand the noise it makes!

It is no problem at all for a rubber lip seal to groove a stainless shaft especially with a bit of help from silt or sand grains which get caught up
in the mix.

Just look at your water pump shaft . Even the oil seal wears a groove in time!!!

 

[Malish]

Sounds like you have some good experience in this. Any thoughts on whether it would be possible to change the lip seals on an old Halyard oil based stern gland?

I'm sure they are just standard items (the code will be stamped on them). The main issue with the Halyard is probably the rubber outer which is most definetly a non-standard item which is no longer available. I swapped mine out (for a Volvo seal) this winter because the seal was slowly dripping oil, I could have put new seals in but couldn't be confident that the rubber outer would last another 10 years (+ the oil reservoir cap has broken and was always a fiddle to empty and re-fill at the end of the season).

 

[Tranona]

It is no problem at all for a rubber lip seal to groove a stainless shaft especially with a bit of help from silt or sand grains which get caught up
in the mix.

Just look at your water pump shaft . Even the oil seal wears a groove in time!!!

I have a Volvo seal that has been in the boat for 15 seasons at least with no wear on either seals or shaft. Unlike a water pump seal the bearing surface is not always the same as the shaft moves backwards and forwards and water never gets past the back of the first seal. In the Volvo design the seals are also greased, and cooled by the water behind them.