Which shaft seal?

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mike_bryon

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I have the Manecraft deep water seal fitted but after 7 years and i guess more than 20K nm it leaks when the shaft is turning so must be replaced. Should I fit the same or are there better alternatives on the market for example, the PSS shaft seal and the Sure Seal?

My gearbox is hydraulic and I do not have a shaft lock so even when sailing the shaft turns.

Can anyone recommend the supplier of a shaft lock?

All advice appreciated.
 
If you can, fit a Volvo seal. Very simple, reliable and cheap. Alternatively if you can't fit it (sometimes the stern tube housing is too big) then a Tides Marine is also a lip seal, but a bit more complicated. Face type seals have fallen out of favour and lip seals are now almost universal.
 
Thanks Tranona

According to Tides marine website the SureSeal is a lip seal type and they sell a spare seal carrier.

The PSS I think is what you call a face type seal.

So it sounds like I should change to the SureSeal
 
Yes, that is correct, Tides has a good reputation and is used by OE builders, particularly in the larger sizes. Volvo seals are made for only one size of tube, so retrofittingis not always possible, whereas Tides will fit different diameter tubes. The problem with face seals is that on the rare occasions they do fail, they do so catastrophically, whereas lip seals slowly wear (if at all) and give plenty of warning. As you say Sure Seal has replaceable seals should you need them, but Volvo has the seals as part of the moulding so the whole assembly needs replacing when worn.
 
mike_bryon said:
I have the Manecraft deep water seal fitted but after 7 years and i guess more than 20K nm it leaks when the shaft is turning so must be replaced. Should I fit the same or are there better alternatives on the market for example, the PSS shaft seal and the Sure Seal?

My gearbox is hydraulic and I do not have a shaft lock so even when sailing the shaft turns.

Can anyone recommend the supplier of a shaft lock?

All advice appreciated.
Click to expand...

The PSS seal is excellent IMO, much better than the Manecraft or Deepsea Seal. The PSS is a face seal but has a rigid S/S collar fitted to the shaft and sealed to it with 'O' rings (as a fixed seal, they don't rotate relative to the shaft) and the seal which is held in a convoluted hose runs against this S/S collar. The difference from others is that a) the S/S collar is easily set at 90 degs to the shaft and b) It has a wider face and allows for more movement on the mounts.

We inherited a DSS (Manecraft) with our last boat and replaced it because the hose was starting to split. A year later and the same thing was starting again, this time we switched to the PSS seal which was an altogether more robust piece of kit. When we sold the boat it had done some 16,000 miles on the PSS with no problems and no sign of wear.
 
Tranona said:
Face type seals have fallen out of favour and lip seals are now almost universal.
Click to expand...

Where did that information come from? PSS seals sell in their thousands. I have one and it is perfectly reliable. I have nothing against lip seals but they do require the shaft to be in near pefect condition. Any nick or scratch in way of the lip will destroy it in short order.

I'm sure many OEMs prefer lip seals as they are half the price of a face seal. But many owners replace their lip seals with face seals when failure occurs.
 
vyv_cox said:
Where did that information come from? PSS seals sell in their thousands. I have one and it is perfectly reliable. I have nothing against lip seals but they do require the shaft to be in near pefect condition. Any nick or scratch in way of the lip will destroy it in short order.

I'm sure many OEMs prefer lip seals as they are half the price of a face seal. But many owners replace their lip seals with face seals when failure occurs.
Click to expand...

Not sure where your information about selling "in the thousands" comes from. Not sure any volume OEM use a face seal. They have a history of unreliability - one design even has a clamp to close it off when it fails. The PSS is better engineered than earlier designs, but it still has the fundamental flaw of relying on pressure of the bellows to create the seal. There are numerous examples in the past of boats sinking through failed face seals. Not so many now because so few are in use compared with other designs. It is true that the Volvo seal is very much cheaper, but that does not mean it is inferior, just the opposite in my view. More complex arrangements such as the Tides Marine and Vetus seals are similar price to PSS.

Over the last 30 years there have been several face seals on the market. They have all fallen by the wayside except the PSS. As for replacement, doubt anybody would replace lip seals - traditional stuffing boxes, yes to get away from drips, and then of course some may choose a face seal.
 
Another vote for the Volvo seal, if your shaft tube is the correct size to take one. I am told that the Volvo seal on my boat is the original one, it is still drip free and the log shows a total reading of about 45,000NM.
I have seen one boat with an adapter specially made to fit the end of an oversize tube and take a Volvo seal.
 
Tranona said:
Yes, that is correct, Tides has a good reputation and is used by OE builders, particularly in the larger sizes. Volvo seals are made for only one size of tube, so retrofittingis not always possible, whereas Tides will fit different diameter tubes. The problem with face seals is that on the rare occasions they do fail, they do so catastrophically, whereas lip seals slowly wear (if at all) and give plenty of warning. As you say Sure Seal has replaceable seals should you need them, but Volvo has the seals as part of the moulding so the whole assembly needs replacing when worn.
Click to expand...
Don't think your facts are right or your wording is excessively alarmist.

Yes, face-type seals have been known to fail - but by no means catastrophically.

Perhaps you'd like to provide your evidence rather than assert your opinion?

I do speak with some experience: of the Bukh seal (not a face type) the Halyard seal and now the PSS seal (for 14 years).
 
The volvo seal is a lovely design. One moulding to replace complex systems that needs very little maintainence. It does however have a design life - 7 years. I know that many older ones work perfectly, but it is a fairly critical component. Depends on your attitude (and potentially your insurers) to routine maintenance.
 
charles_reed said:
Don't think your facts are right or your wording is excessively alarmist.

Yes, face-type seals have been known to fail - but by no means catastrophically.

Perhaps you'd like to provide your evidence rather than assert your opinion?

I do speak with some experience: of the Bukh seal (not a face type) the Halyard seal and now the PSS seal (for 14 years).
Click to expand...

Well I speak from my own experience having been involved in this market in the early days of face seals. They fail for 2 reasons. Firstly as I noted they rely on pressure to keep the faces in contact with eachother. This pressure can be lost for a number of reasons - the bellows fails, it slips up the shaft or in boats with very soft mounts the engine can move forward sufficient to open up a gap. This movement can be either violent engagement of gear or in one cae I saw, water pressure coming up the open tube while surfing. Once that gap is open there is nothing you can do about it, hence the term catastrophic failure. The other cause is something getting caught between the two faces and holding them apart. Same result. It has also been known for the two faces of some designs to stick together through lack of use and get damaged - either scoring the faces or in extreme cases tearing the bellows.

To my mind these shortcomings mean that they are not suitable for marine use because they rely on being set up correctly and not neglected. Whilst it is true that all equipment should be properly installed and maintained, the major difference here is that lip seals, if neglected may wear and slowly weep, but will not fail completely.

The weaknesses are recognised by the manufacturers. PSS quite rightly place great emphasis on setting up the bellows correctly and Manecraft actually have a clamp to lock the seal solid if it fails. Does not instill confidence - for me anyway.

For whatever reason, face seals have not gained a significant share of the market presumably because their advantages - the most significant being they do not wear the shaft, are not valued sufficiently by users.
 
Sorry Tranona but in the circles in which I moved the PSS reigned supreme and I don't know a single person that had any problems or indeed any drops of water pass into the bilges.

The PSS rigid S/S collar seals to the shaft via two 'O' rings and rotates with the shaft, thus no wear on the 'O' rings as they are not moving parts and they will seal on a shaft that is less than perfect. One problem with the Deep Sea Seal (the one with the added 'safety' clamp device) is that it is difficult to set the shaft part exactly at 90 degs and therefore it can run eccentrically. Another is that the hose which applies the pressure on the face is too soft and as we found is prone to splitting over time. The PSS hose is much more robust and the face areas much wider allowing for lots more movement of the engine on it's mounts. The Deepsea Seal relies on a simple hose clip clamp to stop it sliding on the shaft and loosing the adjustment of the face pressure. The PSS collar has a screw fix to hold it in place, plus it is simple to add an extra backstop hoseclamp tight up behind the collar.

I don't know the Volvo seal personally and I'm sure it is good, but I understand it is in limited sizes and not suited to all boats.
 
Volvo seal rec

mike_bryon said:
I have the Manecraft deep water seal fitted but after 7 years and i guess more than 20K nm it leaks when the shaft is turning so must be replaced. Should I fit the same or are there better alternatives on the market for example, the PSS shaft seal and the Sure Seal?

All advice appreciated.
Click to expand...

I fitted a PSS shaft seal before the start of our circumnavigation in 2005, but it never sealed properly and continued to spray a fine mist in use and drip when static. I don't know why, but after 3 months of this, I took it out and fitted a Volvo shaft seal (which we were happy with on our last boat) and it has not leaked a drop in seven years (they are lifed at 5 years). The only maintenance is a squeeze of the only cheap Volvo product in their catalogue, the blue grease every 6 months.

Angus
 
Tranona said:
Not sure where your information about selling "in the thousands" comes from. Not sure any volume OEM use a face seal.
Click to expand...

See http://www.shaftseal.com/en/ (very slow to load but worth it when you get there)

Builders Installing The PSS Shaft Seal At The Factory:
•A.F. THERIUALT & SON, LTD.
•ALDEN YACHTS
•ALL AMERICAN MARINE
•AZIMUT
•BLACKMAN BOATS
•BLACKWATCH (LITTLE HARBOR)
•CAPE ST. MARY BOAT BUILDERS
•CATALINA YACHTS
•CAVILEER YACHTS
•CHEOY LEE SHIPYARDS
•CORRECT CRAFT
•DAWSON BOATS
•DONZI YACHTS
•DUFFY & DUFFY (ATLANTIC BOAT)
•EGG HARBOR YACHT, LLC.
•FOUNTAINE PAJOT
•FREEDOM YACHTS
•FERRETTI
•GLACIER BAY CATAMARANS
•GUNBOAT PTY LTD
•HAKE YACHTS
•HENRIQUES BOATWORKS
•HINCKELY COMPANY
•INDIGO YACHTS
•ISLAND GYPSY (HALVORSEN MARINE)
•JIM LINDELL COMPANY
•KVICHAK MARINE
•LEGACY
•LITTLE HARBOR
•M.B. SPORTS
•MERIDIAN YACHTS
•MAXUM YACHTS
•MENORQUIN YACHTS
•MIKELSON YACHTS
•MODUTECH MARINE
•MORGAN YACHTS
•NICHOLS BROTHERS BOAT BUILDERS
•NORDIC TUGS
•NORTH END COMPOSITES
•NORTHERN MARINE
•ALEXANDER MARINE
•PACIFIC SEACRAFT
•QUEEN LONG MARINE
•QUEENCRAFT (MARINE TRANSPORT)
•RAMPAGE SPORT FISHING YACHTS
•RINKER BOAT COMPANY
•RIVA (FERRETTI GROUP)
•RIVIERA GROUP
•ROSCIOLI
•ROZEMA’S BOAT WORKS
•RYBOVICH-SPENCER
•SABRE CORP.
•SEAVEE BOATS
•SKI SUPREME
•SUNNFJORD BOATS, INC.
•SWAN (NAUTORS)
•SYMBOL YACHTS
•TARTAN YACHTS
•T.P.I. COMPOSITS
•TIARA (S-2)
•TIGE
•TOPAZ BOATS
•TRADITIONAL WATERCRAFT
•U.S.C.G. 47’ M.L.B. (TEXTRON)
•VALIANT
•WELLCRAFT
 
I like the PSS seal, nice and simple but not cheap. Don't listen to the old hokum about "catastrophic failure" it is oft repeated nonsense.
Volvo seals need to be maintained (burped and greased) and are therefore a poor choice if access to the stern gear is difficult. They need to be replaced at fairly short intervals (5 years?).
There have been many florid claims about them on this site, first of all "they never leak", till there was a spate of people having problems with leaks. Then, "they will never fail in the old: "catasrophic way", then one chap said his had split and filled his bilge.
I would have one though, they are inexpensive and a good design, the truth is all stern seals have their plus and minus points, all can fail.
Avoid the PSS if your prop shaft is a close fit in the stern tube, esp if you have a single pot engine with soft mounts.
 
Tranona said:
Well I speak from my own experience having been involved in this market in the early days of face seals. They fail for 2 reasons. Firstly as I noted they rely on pressure to keep the faces in contact with eachother. This pressure can be lost for a number of reasons - the bellows fails, it slips up the shaft or in boats with very soft mounts the engine can move forward sufficient to open up a gap. This movement can be either violent engagement of gear or in one cae I saw, water pressure coming up the open tube while surfing. Once that gap is open there is nothing you can do about it, hence the term catastrophic failure. The other cause is something getting caught between the two faces and holding them apart. Same result. It has also been known for the two faces of some designs to stick together through lack of use and get damaged - either scoring the faces or in extreme cases tearing the bellows.

To my mind these shortcomings mean that they are not suitable for marine use because they rely on being set up correctly and not neglected. Whilst it is true that all equipment should be properly installed and maintained, the major difference here is that lip seals, if neglected may wear and slowly weep, but will not fail completely.

The weaknesses are recognised by the manufacturers. PSS quite rightly place great emphasis on setting up the bellows correctly and Manecraft actually have a clamp to lock the seal solid if it fails. Does not instill confidence - for me anyway.

For whatever reason, face seals have not gained a significant share of the market presumably because their advantages - the most significant being they do not wear the shaft, are not valued sufficiently by users.
Click to expand...
Tranona,

You're whistling in the wind and you know it.

I have found lip-seals considerably less satisfactory than the PSS seal.

The one problem with the PSS is that if you get a rope wrap the shaft can be pulled out dislodging the rotor.

The shaft then moves back when in forward gear moving the rotor from the carbon block.

Even when 12mm from the carbon face, the water coming in is far from catastrophic and easily coped with by a 500gph bilge pump.

The two lip-shaft seals I had produced far more exciting leaks.
 
Shaft seals

Tranona said:
Not sure where your information about selling "in the thousands" comes from. Not sure any volume OEM use a face seal. They have a history of unreliability - one design even has a clamp to close it off when it fails. The PSS is better engineered than earlier designs, but it still has the fundamental flaw of relying on pressure of the bellows to create the seal. There are numerous examples in the past of boats sinking through failed face seals. Not so many now because so few are in use compared with other designs. It is true that the Volvo seal is very much cheaper, but that does not mean it is inferior, just the opposite in my view. More complex arrangements such as the Tides Marine and Vetus seals are similar price to PSS.

Over the last 30 years there have been several face seals on the market. They have all fallen by the wayside except the PSS. As for replacement, doubt anybody would replace lip seals - traditional stuffing boxes, yes to get away from drips, and then of course some may choose a face seal.
Click to expand...

We recently replaced a Deep sea seal which was probably fitted when the boat was new - 25 years ago. It didn't have the emergency clamp which I am told has been standard for the past 15 years. So some of the replies appear to be a bit biased.
 
I suspect, like boats, shaft seals all have their good and bad points and one has to take a view on which will suit ones' needs the best.

In the end those with a Volvo seal will argue vehemently that is the best in the world - others will, equally swear theirs' is the best.

They're all arguing with limited knowledge and maximum prejudice - the Volvo seal should be the most common on new boats, because of the company's marketing policy towards builders. But, as with all things Volvo, you, as the purchaser of parts, will carry the heavy burden of redressing the company's profitability.
 
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