Saildrive diaphragm seal replacement

[Interlude]

There are many references to Volvo recommending replacement of saildrive seals at 7 year intervals (PBO 375 p48, PBO 494 p68, Sailing Today Dec 2003 (which says that originally Volvo said to replace annually, now on a 7 year interval)). There are several articles in PBO describing the replacement process, which requires removal of the leg after splitting the drive from the engine and sliding the engine forward … an expensive and tedious proposition.

I understand that Yanmar Sail Drives differ from Volvo in having a pair of seals with a water leak detector between them. The Yanmar SD20/40 saildrive owners manual says on p15 to inspect every two years (and to inspect the seal sensor every year – and presumably test by immersing into salt water), however the same manual says on p24 to replace the seals every 2 years.

I prefer to follow the advice given by Pat Manley on p71 of PBO 436, April 2003, who reiterates the need to change the seal on Volvo drives every 7 years, but says “(Yanmar doesn’t require a diaphragm change, but the rubber seal on this sail drive system is double-skinned and has a water detector between the skins.) As regards this diaphragm change, I haven’t heard of a serious failure ever having occurred.”

My question of forumites is: has anyone firm evidence of seal/diaphragm failure resulting in either a slow leak or catastrophic failure (resulting in sinking) for either Volvo or Yanmar saildrives? Does anyone admit to having run either Volvo or Yanmar drives well beyond the 7 year interval? I declare an interest as the owner of a five year old Yanmar unit, whose sensor I have checked (once!).

 

[AIDY]

I changed my volvo 120s at 10 years just really for peace of mind. It looked as good as new. my only concern with sail drive units is the two back to back prop shaft seals which i change every 2 years. I caught mine in time a few years back, it could be curtains if the oil drops straight out of the saildrive

 

[Cantata]

I changed my volvo 120s at 10 years just really for peace of mind. It looked as good as new.

Ditto, just a bit grubby as we are in a mud berth. Out of interest I cleaned it up and apart from the date on it there wasn't a lot to distinguish it from the new one.

 

[richardbrennan]

I changed mine at eight years. The diaphram not only keeps out the water, but also acts as the seal that keeps the various channels between oil and water in the leg seperated. There was clear evidence on mine that the cooling water was migrating towards the oil in the leg but fortunately had not made it the whole way. It's probably worth bearing this possibility in mind, although mine may have been an isolated case.

 

[AIDY]

Ditto, just a bit grubby as we are in a mud berth. Out of interest I cleaned it up and apart from the date on it there wasn't a lot to distinguish it from the new one.

It must be the build quality on these S series

It's probably worth bearing this possibility in mind, although mine may have been an isolated case.

 

[oldsaltoz]

.
QUOTE
I understand that Yanmar Sail Drives differ from Volvo in having a pair of seals with a water leak detector between them. The Yanmar SD20/40 saildrive owners manual says on p15 to inspect every two years (and to inspect the seal sensor every year – and presumably test by immersing into salt water), however the same manual says on p24 to replace the seals every 2 years.

Buke sail drives also have a censor between a double layered seal. I think the replacement was around 5 years, but not sure it was a long time ago. Parts cost was a major consideration with and all sail drives, well worth investigating before you go this rout.

.

 

[gianenrico]

Ditto, just a bit grubby as we are in a mud berth. Out of interest I cleaned it up and apart from the date on it there wasn't a lot to distinguish it from the new one.

Changed mine after 15 (ONE FIVE) years, to make boat sale easier; 2 hours work.

 

[Interlude]

OK, so far no one has reported knowing of an actual failure of either Volvo or Yanmar seals ..... or even a slow leak?

 

[Martin_J]

I was just going to start writing about how I'm sure that I had read in the past that someone pushed a screwdriver through one once (by force because it wasn't easy) and the hole nearly sealed itself up again as the screwdriver was taken out....

but then I just came across this story below whilst trying to find the screwdriver one..

http://bellavia.ca/2009/July.html
(read from 'A bump in the night').

It looks from this like the rear engine mounts are quite an important part of the equation. Solid mounts would possibly have prevented the engine from rising.

 

[PeterGibbs]

There are many references to Volvo recommending replacement of saildrive seals at 7 year intervals (PBO 375 p48, PBO 494 p68, Sailing Today Dec 2003 (which says that originally Volvo said to replace annually, now on a 7 year interval)).

My question of forumites is: has anyone firm evidence of seal/diaphragm failure resulting in either a slow leak or catastrophic failure (resulting in sinking) for either Volvo or Yanmar saildrives? Does anyone admit to having run either Volvo or Yanmar drives well beyond the 7 year interval? I declare an interest as the owner of a five year old Yanmar unit, whose sensor I have checked (once!).

The 7 year advice is just that. I follow it so that I have a trail of manufacturer's maintenance should anything arise in that department. As said elsewhere, the Volvo seal serves the unit as well as the hole in the hull -2 reasons to follow Volvo's advice.

The back to back seals at the prop end have no recommended replacement interval, and mine lasted 10 years before I noticed a slick following me, and got the boat hauled immediately for seals replacement. Providing the oil level is maintained in the leg, to restrain the ingress of water, the unit will survive a fews hours of operation to get back to base etc. without damage. If the diaphragm is being replaced it makes sense to pop the prop seals at the same time - a lot cheaper than waiting for them to fail!

PWG

 

[actionoptics]

saildrive prop shaft seals

When I found water in my Bukh gear box, the seals had worn
but so had the sleeve. I well known marine engineering
concern had replaced the seals not long before but had
not noticed the damage to the sleeve so the new
seals did not last very long. The sleeve cost about £90.

 

[Sans Bateau]

I think one or two replies are a little confused as to what seal the OP is enquiring about, I believe it is the diaphragm that goes around the saildrive leg and is also attached to the hull and not the oil/water seals inside the leg.

My diaphragm is the original dating back to 1993, yes I suppose it ought to be changed soon. I once asked a respected local marine engineer what his thoughts were, and he told me that in all his years (30 or so pulling spanners) he has never seen a diaphragm fail catastrophically.

Volvo and others will be duty bound to advise it must be changed at X years, to protect themselves more than anything.

Maybe I'll change mine this year, I'll have a good look at it.

 

[Interlude]

Thank you all - particularly Martin J with the scarey story of what might happen if you ground on the saildrive - more likely on a cat than a keel boat, but possible in either. Yes Galadrial, I was basically interested in the diaphragm seal failure possibilities, as a catastrophic failure of this can have a lot of water in the boat. With a cat, a watertight bulkhead to above the water line would seem like a good idea.

 

[boatmike]

Thank you all - particularly Martin J with the scarey story of what might happen if you ground on the saildrive - more likely on a cat than a keel boat, but possible in either. Yes Galadrial, I was basically interested in the diaphragm seal failure possibilities, as a catastrophic failure of this can have a lot of water in the boat. With a cat, a watertight bulkhead to above the water line would seem like a good idea.

Yes indeed and when building my boat I did just that. If the saildrive diaphragm were to fail it would let in water to the engine compartment which has watertight bulkheads each end. No question of catastrophic failure. Incidentally no, I have not changed the diaphragm and its as good as new after seven years so I don't intend changing it!

 

[quaelgeist2]

why bother ?

The question pops up 2-3 times every year in every decent sailing/boat forum.

No one has ever reported an own experience with a slow or fast failure of the diaphragm on a saildrive.
Many an owner has reported to have replaced what looked like a perfectly kept example of what they replaced in the process.
Mine is 13 years old and unless a future buyer insists on it, I cannot see why I go through an obviously unnecessarily act of maintenance...???

Yes, there are other maintenance tasks where you hardly ever see the benefit yourself. BUt in those cases one knows plenty of people who suffered through lack of maintenance:
- changing oil (boat and car)
- replacing impeller
- changing drive belt
- replacing brake pads/discs

Similar to removing the rig in winter: Do not forget the things that can go wrong when dismantling and reinstalling everything...

Just my 2 cents, do it if you like to.

 

[Interlude]

Shaft seal

So I guess it serves me right to be thinking about the diaphragm seal failure possibility - checked the oil level in the sail drive leg last week to find it full of white oily emulsion - the seal on the prop shaft evidently gone after 5 years and about 350 engine hours. Luckily I was due for the annual slip, antifoul, and engine/saildrive service so hopefully this will prove to be an annoyance rather than a disaster. Rather than an oil slick on the water, the clue was oil on the top of the lower leg of the saildrive (adjacent to the diaphragm seal) - presumably pushed through a breather in or near the dipstick by the sea water pressure of about 0.4 metres of head.

I will be a little more regular in checking the gearbox oil in future.

 

[PeterGibbs]

There are many references to Volvo recommending replacement of saildrive seals at 7 year intervals (PBO 375 p48, PBO 494 p68, Sailing Today

My question of forumites is: has anyone firm evidence of seal/diaphragm failure resulting in either a slow leak or catastrophic failure (resulting in sinking) for either Volvo or Yanmar saildrives? Does anyone admit to having run either Volvo or Yanmar drives well beyond the 7 year interval? I declare an interest as the owner of a five year old Yanmar unit, whose sensor I have checked (once!).

I believe the gaiter on the Volvo 120 leg is not just neoprene, but a combo with internal reinforcing. I work on the basis that, should a failure commence, it would be a minor leak - not dissimilar to a poor stern gland - and containable, not a catastrophic burst with a risk of sinking.

I have never read anything from Volvo supporting this gaiter in detail or giving advice, other than to replace it every 7 years. At least the insignificant reports of problems, even when overstepping the 7 years mark, seem to support faith in this piece of gear! We travel in hope...

PWG

 

[rtchina]

Never disturb a going concern.

 

[Bonobo]

I have a 4 year old SD50. Last week the seawater light and aural warning came on. Book says to turn off engine and sail to port "quickly". So far I have no water in the boat. I have removed and tested the sensor and it's working fine although there was some salt corrosion on the probes. So now what to do. To replace the outer diaphram requires only the removal of the leg. Upper diaphram is much bigger job but doesn't seem to have failed. A friend says we can do it but i'm not too confident. May as well do the oil seals same time. In conclusion, yes the diaphrams do fail and it is stressful when at sea.

 

[RichardS]

I have a 4 year old SD50. Last week the seawater light and aural warning came on. Book says to turn off engine and sail to port "quickly". So far I have no water in the boat. I have removed and tested the sensor and it's working fine although there was some salt corrosion on the probes. So now what to do. To replace the outer diaphram requires only the removal of the leg. Upper diaphram is much bigger job but doesn't seem to have failed. A friend says we can do it but i'm not too confident. May as well do the oil seals same time. In conclusion, yes the diaphrams do fail and it is stressful when at sea.

It almost certainly not a failure at all.

See my reply to you in http://www.ybw.com/forums/showthread.php?466152-yanmar-saildrive-gaiter

Take great care if asking a marine service company to look at the "problem" as I foresee an enormous opportunity for you being comprehensively fleeced.

Richard