Yacht Owners Worst Nightmare


What’s wrong with this photo? Hint: the freeboard is touch low.


Our hearts ache for the owners of this yacht.

We have always been obsessive about risk factors, none of which is bigger than through hull penetrations. They are a flooding risk, maintenance headache, and if bronze, a potential exit point for lightening if you suffer a direct hit.

Have you counted your through hulls? Do you know where they are? Can you get to them? Do you close them when leaving the boat unattended for long periods? And how about fridge and air conditioning plumbing? How secure is it, and what are the unattended risks associated therewith?

As boat owners continue to stretch the complexity of systems aboard, the temptation to riddle the hull with underwater thru-hulls increases.  Owners are often uninformed about the potential problems and risks associated with fittings below the waterline, and many builders and boatyards find it tough to deny the wishes of a paying client.

It does not have to be this way. We are not trying to push our concepts on the back of anyone’s disaster, but there are some systems design principles that will mitigate these risks:

  • Watertight bulkheads, in particular around the engine room and shaft logs.
  • Single incoming salt water point with easily accessed valve to turn off when leaving the boat.
  • Fridge and air conditioning cooling systems that do not rely on pumping salt water through the condensing coils.
  • Standpipes for below the waterline fittings with shut off valves above the waterline (fiberglass and metal construction).
  • Dual automatic bilge pumps in high risk (engine room) areas.


Posted by Steve Dashew  (February 11, 2011)

12 Responses to “Yacht Owners Worst Nightmare”

  1. Kent Says:

    At least it sank at the dock and not in the middle of the ocean.

  2. Ben Says:

    Hi Steve,

    Great article, I wish more people would think like this, I have two seacocks onboard, sink out and galley salt water in. Keel cooling deals with the engine, and the toilet is a chemical toilet, Simple, Even better if I could run the sink outlet out above the waterline…

    I am glad to see that you also encourage a simpler approach, athough not quite as crudely as mine.. Many of your ideas have been pretty groundbreaking especially to budget sailors like myself, but athough most of us with smaller heavier boats will struggle to weather route as well as you do, we can try to avoid the very worst by applying the same principles. Thanks for all your work over the years.



  3. Matt Marsh Says:

    Ouch. I would not want to be the insurance agent, surveyor or dockmaster who has to deal with a situation like that, let alone the owner.

    I’m trying to remember the statistic on how many boats sink at the dock- I seem to recall it’s well over half of all sinkings- virtually all of which could be prevented with a bit of thoughtful design and preventive maintenance. Little things, like checking the seacocks now and then, cleaning up the bilge pump system (both the fluid and electrical sides), and replacing hoses when they start to get soft, could go a long way towards reducing these incidents- and therefore insurance rates.

    There was an interesting discussion last week about watertight bulkheads on the Morgan’s Cloud site, the conclusion being that just about all serious boaters consider multiple watertight bulkheads essential. At the very least, cruisers seem to want the forepeak and engine room isolated from the cabin. I’m quite sure that WT bulkheads can be done, well, without messing up the interior layout or adding appreciably to the final price tag, and I see no good excuse for omitting them.

    On the bilge pumps note, I still see those little “600 gph” pumps (that actually move 200-300 gph) all over the place. A one-inch through-hull a metre or so (3′) below the waterline can let in nearly five thousand gallons an hour if it blows. The backup bilge pump needs to be sized accordingly, and needs an impossible-to-ignore alarm. Until we perfect Star Trek’s emergency forcefields, a badly leaking boat’s only chance of survival is for it to make such a racket that the dockmaster comes over to find out what’s wrong.

  4. Matt Marsh Says:

    (correction to the above- that 5000 gph figure is for a 1.5″ through-hull, not a 1″, which would be around 2500 gph.)

  5. Rick de Castro Says:

    We ‘lost’ a boat (Alberg-35) at the dock in Marina Del Rey when I was a kid (40+ years ago)….the seacocks were not maintained, and so were impossible to close…the water inlet for the head (no holding tanks back then) was a piece of garden hose (not sure how old it was) that cracked from age.

    In thinking about it, I find it amazing how many through-hulls that boat had: Two for the head (in and out), one for the galley sink, one for the sump drain, two for the engine (raw water intake, exhaust – but that was above DWL. Aside from leak potential, all the drag the scoops and strainers caused!

    In retrospect we should have recognized that the water around the head was not normal. It’s easy to discount water under a porthole or vent however. And since I’d be at the boat weekly pumping the bilge (manually, with a horribly installed pump) my complaints about the water (I was 12 and 13, I think) were discounted. Whoops.

    So, one winter when nobody had been at the boat for several weeks, we got a call from the harbor patrol. Funny that nobody else on the dock, at the club, noticed the boat getting lower and lower….and of course, past a certain point the lower it got the more openings for water to enter there were.

    The insurance co salvaged the boat, some guy bought it and fixed it (basically rebuilt the interior including the wiring, since it had all been soaked, the oiled teak bulkheads were ruined, etc…) and then tried to sail it up to the Bay Area. IIRC, he foundered around Pt. Conception, tried to cut the point short and the current got him on the lee shore. He got off OK but the boat was totaled for good.

    I like the idea of externally plugging the through-hulls when leaving the boat for some time. I like the idea of very few hull penetrations even more.

    These days I rigorously maintain my through-hulls (Marelon is easier than bronze, of course), they get shut off when not in use, and all the hose is double-clamped marine grade.

  6. Mike Says:


    I liked the idea of running your a/c units with fresh water. Is there an optimum water tank size for a given a/c unit and the raw/fresh water circulation system? We would be trying to run a 9,000 BTU unit with a 80 gallon tank.

    This may also be an idea for folks with older cruising boats. We are going to add extra glass in the area below the v berth to seal things up and then add water tight hatches under the mattress. Should give an area below the water line that stretches aft about 9 feet from the bow and reaches a depth of 4 feet… Maybe not the ideal watertight bulkhead but it’s better than nothing and not to expensive.

  7. Steve Dashew Says:

    Howdy Mike:
    Using the fresh water tank for air conditioning is very much an experiment. It is easy to do with a metal boat, but tougher with GRP and its insulating properties. My guess is that it would be difficult to get this to work for any length of time in warm water. But give it a try, and let us know how it turns out.

  8. Ben Says:

    Hi Matt,

    With all respect I don’t recall the conclusion to the discussion at morganscloud.com being that watertight bulkheads were essential, But more that they are a very good idea, If I had considered them essential, I wouldn’t have taken Snow Petrel down to Antarctica, with only a couple of crudely sealed half bulkheads under the fwd Double bunk. Do what you can with what you have… But I agree that we should Definitely give them more consideration on new designs.

    Many fine seamanlike and safe voyages have been made by small vessels with no or minimal WT bulkheads. The bigger the vessel the easier they are to incorporate, and the more important they are, On the Dashews sized vessels they definitely make lots of sense.



  9. Steve Dashew Says:

    Hi Ben:
    I agree, you can go long distances without watertight bulkheads. We did a circumnavigation without them, and had 22 throughhull fittings. But it was always a source of worry. Consider a sheet wrapped around the prop, pulling the P-bracket loose. No bulkhead and you probably sink. Or being aground and having the rudder work a hole in the aft end of the boat. Shipping containers, logs, etc. make it really nice to have a forward watertight.
    Production builders could easily incorporate these at minimal cost, if the buying public demanded it.

  10. Ben Says:

    Hi, Just been thinking my last post might have come out abit wrong, I agree with Matts post, and all the others on here, but just thought the word essential was a bit stronger than I would have put it…

  11. Ben Says:

    Hi Steve,

    Whew 22 throughhulls, and I have trouble keeping track of two.. Interesting thought about the buying public not demanding it, also considering the sadlers and etaps have had unsinkable boats for years, and they have not really taken off as a concept. Neither has the float pac idea. so maybe much of the buying public seem more concerned about bunk space and drinks holders than sinking…

    How do your boats trim with various WT compartments flooded, are they still sailable with the bow flooded, or do you flood the stern to compensate?

  12. Steve Dashew Says:

    Hi Ben:
    With the forepeak flooded there would not be a major impact on trim. The center of the FPBs (under the great room) have fuel tank tops right around 1/2 load WL, so not a trim problem here. The sleeping areas have their cabin soles about 210mm/8.5″ below DWL (half load), so there could be some significant volume of liquid creating problems in these areas. However, we are talking roughly 2/2.5 tons of ocean between the tank top and half load waterline, which the boat could stand, depending on sea state. But the dynamic impact of this rushing back and forth in a seaway would probably wipe out the interior, and in big seas the forces generated would be substantial. Which is why there is 12mm bottom plate in the first place! There is also a collision bulkhead roughly three feet/.9m back from the bow.