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Old 06-01-2020, 05:15   #1
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Prevalence of catastrophic saildrive seal failure

A frequent comment on this forum regarding choice of “new” boat relates to type of propulsion, saildrive versus shaft. Contributors frequently dismiss saildrives for not wanting a big hole in the bottom of the boat. Although I’ve never read of a catastrophic failure of a saildrive seal or even leaking of a seal, curious if anyone has any data, experience, etc., with this and how it was managed.
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Old 06-01-2020, 05:30   #2
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Re: Prevalence of catastrophic saildrive seal failure

Neither have I. I saw a catamaran in the slings that had sheared off the complete lower saildrive leg after hitting a semi submerged log and and the diaphragm remained intact and watertight.
Does anyone reading the thread have any first hand knowledge of saildrive diaphragm failures?
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Old 06-01-2020, 06:22   #3
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Re: Prevalence of catastrophic saildrive seal failure

Yanmar sail drives have a "water in leg" sensor.
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Old 06-01-2020, 06:46   #4
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Re: Prevalence of catastrophic saildrive seal failure

If you search the forum you will find a couple of instances of sail drive seal failures. One was in Thailand if I remember correctly where a Lagoon cat got a line wrapped around its prop that was tied on a cleat and managed to rip the drive and engines off its mounts and flood a hull. This happened because the water tight bulkhead had been compromised. In another instance a whale surfaced under an FP cat off of Bermuda and both drives were ripped from their mounts and resulted in flooding of the engine compartments but no flooding of the boat due to intact water tight bulkheads. It also destroyed the rudders and the boat was abandoned due to an inability to steer. I personally once snagged a submerged lobster pot line(attached to a string of 10 pots) at 8.5 knots and was dragged to a stop almost instantly. It did nothing to the sail drive or seal. On the other hand I once wrapped up a crab pot line on a shaft drive which broke the shaft coupling and pulled the shaft back about 2 feet, jammed the rudder, broke the stuffing box, and resulted in significant water entry. Stuffing lots of stuff in the hole saved the boat ( reduced the water flow to the point the pumps could keep up). In my personal experience I have no worries about the sail drive seals.
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Old 06-01-2020, 07:01   #5
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Re: Prevalence of catastrophic saildrive seal failure

Captain Bill, I'm flabergasted. It sounds like

1. You sail around a LOT of crab/lobster traps, and

2. Whoever rigged that crab pot was tired of having his lines cut, and

3. You can get yourself out of just about any "catastrophic" failure.

Bravo!
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Old 06-01-2020, 08:07   #6
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Re: Prevalence of catastrophic saildrive seal failure

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Originally Posted by tkeithlu View Post
Captain Bill, I'm flabergasted. It sounds like

1. You sail around a LOT of crab/lobster traps, and

2. Whoever rigged that crab pot was tired of having his lines cut, and

3. You can get yourself out of just about any "catastrophic" failure.

Bravo!

Well the crab line I hit at night was painted black or very dark blue, but in any case I couldn't see it. The lobster pot was in Maine and the float had been pulled just under the surface by a very fast outgoing tide. If you go to south Florida or Maine you cannot help but sail around a bunch of crab/Lobster floats. The shaft drive incident happened in 1984 and the sail drive incident happened in 2015. All that proves is that I'm old.
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Old 06-01-2020, 10:21   #7
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Re: Prevalence of catastrophic saildrive seal failure

For what it's worth.....
As a former Volvo & Yanmar dealer.
Some sail drive manufacturers use a double diaphragm seal system for "safety".
Periodic replacement of the diaphragm is normally part of the routine planned maintenance as per manufacturer's specifications and if carried out correctly there is very little risk of water ingress except by unforeseen major events.
The very early Volvo sail drive diaphragms had some premature failure issues in hot salt water ( Caribbean ) but they were solved many decades ago.
Almost everything technical is a compromise between various factors and the purchaser just has to decide which compromises suit them best.
A way to avoid all of the engine propulsion issues is simply to learn to sail well and have no engine - it is time proven over thousands of years but usually frowned upon in today's world!
Cheers,
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Old 06-01-2020, 10:28   #8
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Re: Prevalence of catastrophic saildrive seal failure

In response to a similar question to the X-Yachts Owners Association (XYOA), which consists of about 100 boats with a mix of Volvo Penta and Yanmar engines all with saildrives, no owner said they had experienced a catastrophic diaphragm failure. The owners who replied reported preventative replacement at 7 years with a spectrum from 5 years to 15 years. Most owners were concerned about keeping to the manufacturers' maintenance schedules to ensure insurance coverage in the event of a catastrophic failure resulting in a boat sinking.
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Old 06-01-2020, 10:38   #9
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Re: Prevalence of catastrophic saildrive seal failure

For me the issue is similar to gas safety, it is not whether it happens or how often but the fact thst it introduces a weekness. In the case of gas I can see positive benifits and many people are happy with the risk. With legs the advantages over a conventional shaft are less clear. If there is no overwhelming advatage to having a leg why take the risk however slight?
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Old 06-01-2020, 11:09   #10
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Re: Prevalence of catastrophic saildrive seal failure

Had a SD seal fail. Water got maybe a foot deep in the engine room. Got the starter but no other problems. I had the valve between the engine room closed so no water into the main bilge.



Was in Chiapas, MX and the travelift could not handle the beam. Had to put on the beach and wait for the tide to go out to remove the SD. Got the seal replaced and back in the boat before the tide came back in. This SD was about 10 years old.


Total PITA but not that big of a deal. If this had happened at sea would not have be catastrophic. Key is having the watertight bulkhead between the engine room and rest of the boat.
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Old 06-01-2020, 11:16   #11
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Re: Prevalence of catastrophic saildrive seal failure

I had the good fortune to speak directly with a few of the technical folks at Volvo at the recent Miami show. I asked about preventative maintenance/periodic replacement of the gasket of the saildrive on our Tartan 47. Their opinion was to just keep an eye on it to see if it was deteriorating. They suggested that I also run my finger along the gasket to see if material was easy to rub off - much like one examines engine belts. If the gasket was not leaking or deteriorating they suggested I go forward with my life and enjoy my boat.
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Old 06-01-2020, 11:39   #12
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Re: Prevalence of catastrophic saildrive seal failure

Just last week I removed the SD40 out of my X by also moving the 4JH3E forward a foot or so. Plan is to do so some proper maintenance on the SD including repainting the leg, replace the seals, fit a kit to prevent cone slipping and renew oil seals, and some other mods.

My X was built in 2002 and I bought her in 2010. I don't think the seals have ever been replaced. What struck me was that the seal came out looking more or less as new, and what a solid piece of rubber it is. Nevertheless I will renew it. The hole in the bottom of the boat is indeed rather large, but most of it is filled by the SD and the rest by a very chunky, very well secured piece of solid rubber. I have every confidence in the design.

For interested folk, to make the engine move easy to do I built two removable runners which fully carried the engine weight allowing the engine to be easily swung forward. Time allowing, I'll generate a pdf with details at some point, mainly for the benefit of any future owner (will be a while before that happens), but can share here later when all is done.
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Old 06-01-2020, 13:40   #13
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Re: Prevalence of catastrophic saildrive seal failure

I had previously owned a catamaran with two Volvo Penta saildrives. We did a lot of rough water sailing, gales and big seas in high latitudes, including sailing north of the Arctic Circle to south and around Cape Horn and many North Atlantic gales and hove-to in high seas.

When sailing from Mar del Plata, Argentina to Rio de Janerio, Brazil, during a strong southeast wind and large seas, I noticed seawater beginning to collect in the starboard engine compartment. I would sponge up about five litres every 12hours. As I watched, every time a large wave passed under the boat from the quarter a small squirt of seawater would come through the diaphragm as the flexible engine mounts flexed with side pressure on the saildrive leg.
The diaphragms/saildrives were about 12 years old.

We were still 500 miles from our destination, but kept going and I checked every couple hours to make sure the squirt did not get worse. When the weather moderated it stopped altogether.
We hauled out in Rio and changed that diaphragm.
The one removed had a small crack in the rubber at one of the folds.
When returning to our home port we changed the other one.
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Old 06-01-2020, 13:50   #14
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Re: Prevalence of catastrophic saildrive seal failure

Worked on a friends boat where we replaced a slowly leaking SD seal . Relaunched twice because still leaking . Eventually found that a previous shipyard job to replace seal had been done with chisels and steel wedges to break the seal free causing gouges and serious scratches that the seal couldn’t cope with , so some plastic weld epoxy and a skim of the face later all good no leak . Moral of story watch what your yard workers are doing with these important seals , check them as soon as u go back in water after any work on seal/or skin fitting.
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Old 06-01-2020, 13:51   #15
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Re: Prevalence of catastrophic saildrive seal failure

Quote:
Originally Posted by Paul Howard View Post
I had previously owned a catamaran with two Volvo Penta saildrives. We did a lot of rough water sailing, gales and big seas in high latitudes, including sailing north of the Arctic Circle to south and around Cape Horn and many North Atlantic gales and hove-to in high seas.

When sailing from Mar del Plata, Argentina to Rio de Janerio, Brazil, during a strong southeast wind and large seas, I noticed seawater beginning to collect in the starboard engine compartment. I would sponge up about five litres every 12hours. As I watched, every time a large wave passed under the boat from the quarter a small squirt of seawater would come through the diaphragm as the flexible engine mounts flexed with side pressure on the saildrive leg.
The diaphragms/saildrives were about 12 years old.

We were still 500 miles from our destination, but kept going and I checked every couple hours to make sure the squirt did not get worse. When the weather moderated it stopped altogether.
We hauled out in Rio and changed that diaphragm.
The one removed had a small crack in the rubber at one of the folds.
When returning to our home port we changed the other one.
Thanks for the report. Aren't these typically two layers? If one layer was a crack in a fold, do you know how your 2nd layer was compromised?
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