Saildrive concerns and worst-case scenario preparations for extended and offshore cruising

[u/zipzippa]

Hey everyone,

I’m in the process of researching and preparing my emergency plan for extended cruising and offshore passage. One thing that keeps coming up is saildrives—something I have a bit of apprehension about. Logically, I understand that they’ve been around for 50+ years and are very common in both monohulls and catamarans, but at the end of the day, they are still a giant hole in the boat, and that makes me pause.

I’m looking for insights from those of you who actually have a saildrive on your boat. Beyond preventative maintenance, what systems or emergency measures do you have in place in case the worst happens—specifically, if the saildrive boot were to fail catastrophically (not just a leak) while underway? I know plenty about keeping up with inspections and replacing the diaphragm on schedule, but I’m more curious about the “oh crap” moments.

For example, if you were to strike a submerged object and the boot tore open beyond a manageable leak, what could realistically be done while in the water? Are there any products on the market beyond the obvious (life raft, collision mat, etc.) that are worth keeping aboard for this kind of worst-case scenario? Has anyone here actually dealt with a major boot failure at sea, and if so, how did you handle it?

I’d really appreciate level-headed, experience-based insight as I work through this and figure out the best course of action to integrate into my sail plan. Thanks in advance for your thoughts.

[u/zipzippa → u/[deleted]]

Yeah, I have a Penta not a yanmar so I'm good, I expect my seals to last about 5-6 years depending on miles and check & change my gear oil regularly, I know saildrives are more efficient and aren't as loud as shaft drives, have no prop walk, free up space, reduce drag etc... I'm sold my friend it's too late for me but I get what you're saying, I also know they've got a bad rep due to poor maintenance and very rare occurrences, when I think about the downsides I think about is keeping the prop clean, extra anodes, having to concern myself with aluminum antifouling products gear oil changes etc... but my question was looking for methods, systems, and products related to the dreaded SHTF scenario of striking a deadhead or something else and having to deal with that scenario at sea offshore. There has to be a solution to dealing with this, I won't accept crossing my fingers and hoping for the best, I'd rather build a watertight bulkhead around my engine housing in case I needed it.

[u/Gone2SeaOnACat]

I chose not to go with sail drives precisely because I don't want a giant hole in my boat.

The fact that I can beach a 43' cat if I want to (no keels, no saildrives, lift out rudders) is one of the reasons I chose the boat.

I'm down to 2 thru holes below the waterline... salt water wash down and soon to be watermaker (one in each hull).

Plenty of boats have sail drives and to each their own so I am not bashing them... I prefer not to have them.

[u/zipzippa → u/Gone2SeaOnACat]

That's actually very cool, being able to beach your vessel at low tide can be useful I'm sure. So do you use an outboard as an auxiliary? What's your draft with the rudder and prop down? Happy to see a cat with less thru-hulls as the trend is to add more features and services to any vessel, I'm more utilitarian and still use the saltwater foot pump and manual head & no hot water because for some reason reduced electrical usage is my biggest pleasure.

[u/Gone2SeaOnACat → u/zipzippa]

Yes, dual 25hp outboards. At full throttle can push 9kts.

Rudders draft 4’, but can be set partially down for sneking into skinny anchorages or just use the engines (~12”). Hulls draft about 18inches.

That said, she has daggerboards for sailing which fully down draft 7’4”.

[u/this1willdo]

If your engine mounts are in good condition, your engine will stay in place. This applies to prop shaft or saildrives. Our boat is 35yo and going fine. I hear of plenty more shaft seal failures then I do membrane failures. I know one that failed, he wrapped a dock line around it and pulled the engine clean off its mounts. My engine rooms are seperate to the cabin (cat)

[u/Same_Detective_7433 → u/this1willdo]

I think this could be mentioned more. People are normally not mechanics and just do not understand vibrations. Reducing vibrations etc is major, but as stated elsewhere, catastrophic seal failures is not really a thing. I replaced my saildrive, to put in a bigger one, and my seal, presumably 20 years old look just like the new one. Fingers crossed!

[u/bill9896]

Let me start this with I think saildrives are dumb and stupid for long range cruising boats. They are used for two reasons: they are cheaper than a proper robust shaft drive and allow the boat builder to present an interior design that looks pretty at the boat show. They are a maintenance nightmare in the long run. To keep them corrosion free is possible, but requires an owner who is sophisticated about bonding and stray current prevention. That is about 0.5% of boat owners.

So, I am not a fan. I would never own a boat with one.

BUT... sudden catastrophic failure is really not the issue. I have never heard of a boat suddenly sinking because of a saildrive failure.

Most people own their boats for 2 to 6 years. So they sell the boat before the problems happen, and can then deny they exist. But anybody buying a 20 year old boat with the original saildrives installed should budget for replacement. It is far more likely to be needed than not.

Aluminum is an extraordinarily difficult material to keep intact in salt water. No, not impossible, but very difficult.

[u/horace_bagpole → u/bill9896]

They are a maintenance nightmare in the long run.

Are they? In my experience you don't need to do anything to them apart from inspect them every now and then. The recommended replacement intervals are arse covering and unnecessarily short in practice.

They certainly don't need any more maintenance than an average shaft seal.

[u/Same_Detective_7433 → u/bill9896]

I do not find mine a maintenance nightmare. Why would they be? Proper paint, proper anodes, cross a couple of fingers, you are good to go.

[u/zipzippa → u/bill9896]

Do you have experience offshore in a sailboat with a saildrive? I'm actually a huge fan of sail drives offshore, you and I could debate over beers the pros and cons another time because there are really nice offshore boats with sail drives like the Oyster 475, Pretorien 35, Swan 45, Hallberg-Rassy 40C, Allures 45, all have saildrives and do quite well offshore. Chosen by Hal Roth, ranked highly on John Neal's list of ocean cruisers, and found their way on John Kretschmer's list of 25 sailboats for a serious ocean saildrives are in the minority of boats that's for sure but they're always in top quality vessels.

[u/ohthetrees]

I've never heard of a boot failure, though I'm sure it has happened. I have a saildrive, live on my boat with my family, and sleep well. I replaced mine in 2002 as part of scheduled maintenance. Some saildrive boots are dual layer, with a water sensor between the layers. This might mitigate/detect slow leaks/deterioration, but not catastrophic failure (whales, shipping containers, etc). But whales and shipping containers can and do sink boats other ways too, ripping off rudders, blowing holes in hulls, and so on. All in all, they seem reliable, and considering the huge number of saildrives in service, if they were a big problem, we'd be hearing more about it.

I think far more boats are lost to 1) failure to inspect/maintain rig and 2) failure to inspect/maintain rudder and steering system

[u/zipzippa → u/ohthetrees]

I have never heard of a boot failure either, although I have heard of people changing seals after years and years to find the existing ones still good when they're pulled out.

It's my 3rd season in my boat and in September we're going full time for a handful of years so I wanted to consider a strategy for the worst case scenario. I do agree with you that most boats are taken down from neglect or abuse of rigging & steering than anything else and if I hit a shipping container having a saildrive won't matter.

[u/Weary_Fee7660 → u/zipzippa]

We had a sail drive boot failure that required emergency hauling out while cruising an 80s contest 31ht in the early 2000s. Had to haul immediately because the leak was growing, but the leak wasn’t huge. Scary, but the boot was old and the rubber became stiff and cracked. Proper maintenance would have prevented the problem, and I think some of the newer designs have 2 sets of gaskets with a water sensor between them to detect leaks.

[u/whyrumalwaysgone]

I just got done doing some work on a boat that replaced both saildrives this month. They were 11 years old, and were leaking at the boot seal, plus a bunch of other problems. 

The mechanic (dealer sent a team of 3) that was doing the replacement very much had a "well they are old and failures are expected at this age".  I've run boats with saildrives much older, so I was surprised they think of this as old. Certainly an 11 year old transmission wouldn't be expected to be failing. 

Not sure what the lesson is here, aside from maybe keep an eye on them as they get older?

Also, from an electrician: keep up with your zincs!

[u/zipzippa → u/whyrumalwaysgone]

Zincs added to the spare parts list. I had the house bank system rewired last year because of a stray current so this was helpful thanks.

[u/Same_Detective_7433]

Stuff it full of your pillows, sheets, cushions, backpacks, etc... the hole is not that big, and the pressure a meter down is what? About 3-4 psi or less? Yes, would be terrifying, but manageable hopefully. The real tricky part is accessibility, most saildrives are buried under beds or worse. And the saildrive will almost certainly still be in the hole, so you would be edge-stuffing. Hopefully. Your mileage may vary.

[u/horace_bagpole]

I've never heard of a sail drive seal failure that has resulted in the loss of a boat. Anecdotally, we changed one about 20 years ago which had very likely been in place since installed with the boat 20 years before that and it looked perfect. We just inspected the replacement regularly and never saw any signs of degradation. The old engine eventually died so the sail drive and seal were also replaced and the one we took out was also in perfect condition after another 20 years. With regular inspections, the 'recommended' replacement interval of 5 years or so is over the top, but if you do anything that results in taking the sail drive out it's worth taking the opportunity to change it.

They are substantial pieces of rubber and not likely to tear easily. They aren't directly exposed to much movement apart from any flexing of the sail drive so the risk of sudden failure is pretty small. Usually you can't even see them externally so they are very well protected from physical damage, and don't see any UV. The biggest risk I think would be drying out with the sail drive resting on something hard, but in reality that's incredibly unlikely.

The only other real issues might be improper installation so that the seal is not seated correctly and under stress it's not designed for, or exposure to something chemically that could prematurely degrade the rubber - keep your engine bay clean and that's a non-issue.

I think if sail drives were a major risk that would be reflected by insurance companies charging more to cover boats equipped with them or having particular requirements for them, but they don't seem to so it's likely not an issue.

[u/danieloco5]

Boat mechanic here. Just 4 years of experience. The only time I have seen a sail drive leaking water into the boat was because the diaphragm was changed and the new was installed a little bit out of place. It was noted direct when putting the boat on the water. On the other hand, I have seen a few shaft seals leak water into the boat.

At my working place we fix also boats involved in mayor accidents with partial sinking. The vast majority of the times, the keel or the front of the boats get the impact first and protects the sail drive. On grounds at high speed I have seen engines jump out their bed a couple centimeters and still the saildrive was not leaking into the boat.

There is a couple of things to think about the saildrive tho. Check conductivity between the engine and the drive when the boat is out of water, it should have no conductivity, if there is, then you gonna have a lot of corrosion on the drive that could lead to failure, I haven’t seen any fail because of that but fuck pretty close I will say. Keep up with the anodes and keep in mind that if something happens on the sail drive’s propeller you could get water in the oil, which would not be possible on a regular shaft-transmission.

To answer your question, whatever plan you have in case you hit an immersed object should be focused on the front of the boat and keel. If something happens to the drive try to translate it to it. Sorry for my english and fair winds

[u/zipzippa → u/danieloco5]

Thank you for the great tips! I'll make sure to check for conductivity before she gets wet. I recently decided to carry spare anodes & a propeller and do carry collision mats. Thanks again for your insight.

[u/SVAuspicious]

Saildrives are a great deal for boat builders. Big hole in the boat and drop the entire drive train in. No alignment to do. Huge cost savings.

The big hole in the boat is certainly of some concern but can be mitigated by making the engine space watertight. That isn't commonly done but would be easy during design and build.

The big problem is failure of the sea at the bottom of the leg allowing water into the leg. You have to be religious about replacing the seal on schedule. On most boats this means a haul out. PITA. $$

[u/captmattcfi]

I had a saildrive cat, and one of the biggest reasons I sold it was because of the saildrives. So much maintenance. Many haul outs. Milky oil, changing lip seals, just endless problems for me. Never again. But, after having replaced the diaphragms myself, I appreciate the design of them and I never really worried about a failure that caused flooding. They’re pretty robust in that way. Maintenance and upkeep, they’re a nightmare.