Mitigating the Threat of Sail Drive Seal Failure

[schoonerdog]

is there a way to mitigate the threat of a saildrive seal failure? Some steps, something to carry, that would help should you bump something really hard and tear a seal?

[Captain Bill]

On some boats the engine rooms are isolated by waterproof bulkheads to a bit above the waterline or completely. That way if the saildrive seal, or for that matter any engine room through hull fails, it only floods the engine room up to the waterline. Actually it's a bit higher than the normal waterline since you loose the bouyancy provided by the engine compartment. The engine electronics are probably toast but you don't loose the boat.

[colemj]

Well, you can rest easier knowing that it is a very rare occurrence - I haven't been able to find one example of it.

A failure due to puncture or small tear will probably be mostly self-sealing and a very slow leak.

I don't think a bump will be enough to tear a seal. You would need a good twisting motion - one that would liberate the saildrive from its mounts.

Someone else told me they carry cans of expanding spray foam and plan to spray it into the cavity if a failure occurs, with the hope that the foam will mitigate the leak enough to carry on to proper facilities. I remember reading of one other person who filled the cavity with 2-part foam while on the hard, but I think this is asking for trouble down the line when you might need to remove the drive.

Mark

[Captain Bill]

I am aware of only one example recently and that was last year when a whale surfaced under an FP cat and tore the saildrives out as well as the rudders. Fortunately FP Saildrives and rudder posts are in isolated compartments and while the boat was disabled it was not in danger of sinking.

[schoonerdog]

I think that FP was abandoned at sea, picked up by a freighter (which hit the boat and dismassed it), and was found later still floating (barely). Our boat has engines amidships. I just hate knowing that I can't fix something should it break. On the plus side, it is rare. Our saildrives are actually at a 45 degree slant between the hulls, so they are extremely protected by the keels. In order for something to hit it, we would have to go over something that would protrude up and between the hulls.

[Jim Cate]

G'Day All,

Here's one case of such an accident:

Last year, good friends in a Seawind 1200, at anchor in Whangaroa harbour, New Zealand, calm conditions, no worries... But during the night they swung over a pinnacle rock that had gone undetected, and the descending tide and a little swell contrived to bounce the boat so that it landed on one saildrive. They awoke to an odd noise and rapidly rising water in one hull (no watertight bulkhead for their engine compartment). Quick investigation revealed that the whole engine had been punched up, shearing the seal and breaking the aft motor mount. The boat was suspended on the leg of the drive, and was not easily moved with the other engine. Towels were jammed in to slow the flow, and the dinghy used to push the boat sideways off the rock. Fortuitously, when the engine dropped back down, the towels were trapped in such a way as to form a reasonable seal, and the pumps were able to deal with the water. Hurried communcations found that the nearest facility able to lift them on short notice was in Whangerei, a considerable distance away. A bit daunting, but little choice, so off they went, carrying an engine-driven pump borrowed from the local VMR chaps just in case. Turns out that they made it safely and that the towels continued to serve their purpose, so a happy ending to a very scary episode.

This sort of thing may not be common, but IMO rules out saildrives for a serious crusing boat... at least it does for us!

Cheers,

Jim and Ann s/v Insatiable II lying Cairns, Qld, Oz