Master Blaster

By far the biggest disappointment of my recent new-boat buying experience was when new Lunacy’s engine flooded in the middle of the Atlantic as I was sailing her back from France this past spring. My initial reaction, as I described before, was one of abject denial, though the problem was not at all unanticipated. In fact, prior to leaving, I had asked Jean-François Eeman, managing director of Boréal, point blank if they’d ever had any flooded engines on their boats. He answered there had been only one, on a boat where the buyer had asked that the footwell in the cockpit be lowered 4 inches so there’d be more standing room under the hard dodger. This in turn had required that the raised loop in the exhaust run, just under the footwell, be lowered accordingly.

My anticipation of the problem was hard earned. I have now owned four different offshore-capable sailboats, and of those three have had engines that flooded (or almost flooded, repeatedly, in one case). In a fourth case a large schooner I was crewing on, during my very first transatlantic passage, also suffered a flooded engine. As I like to tell people: I get flooded engines the way most sailors get dirty fuel.

Boréal’s initial reaction to the problem on new Lunacy was much the same as mine. They told me this could not have happened and seemingly wanted to pretend it was a one-off supernatural event, never to be repeated. I could appreciate this, as they have many more boats to worry about than I do. Before seriously considering their responsibility they wanted to understand the cause of the problem, as of course did I. But it is very hard to determine after the fact what precipitated an event like this, unless you can reliably duplicate it, which I most definitely did not want to do.

To restate the simple facts: we had discovered Lunacy’s engine was full of water after sailing closehauled, on both starboard and port tack, for over two days in wind blowing from 25 to over 30 knots, with gusts to over 40. Conditions were certainly rough, but not extreme, throughout this period.

As soon as I dope-slapped myself and accepted what had happened I checked the siphon break on the intake side of the engine’s raw-water circuit, at the top of a raised loop feeding into the exhaust from the heat exchanger. This is actually easy to do on the Boréal, as the plumbing here is perfectly transparent, and I saw immediately the siphon break was functioning normally, with big chunks of air in the line either side of it. Indeed, I have checked the siphon break many times after shutting down the engine since then, and it has always worked perfectly. These siphon valves do sometimes clog up with salt, which is something to look out for, but so far I have yet to see any evidence of such a failure on my boat.

I believed from the beginning the water probably entered the engine through the exhaust side, though Jean-François Delvoye, the boat’s designer, initially declared this was impossible. JFD, as we Boréalists refer to him, had some grounds for his assertion. The exhaust run certainly seems well defended, as there is both a nice raised loop and a waterlock box between the hull outlet and the engine. BUT that outlet is on the side of the boat, the port side, directly athwart the engine, rather than at the stern, and is just barely above the waterline. (The boat’s muffler, installed under a berth in the aft port cabin, is just inboard of the exhaust outlet.) Also, the raised exhaust loop rises not to the highest part of the boat’s deck structure, which would be the deck itself, but to its very lowest part, which is the cockpit footwell, and is also a bit off centerline, positioned a foot or more to port.

As for the waterlock, according to JFD it is sized to accommodate twice the volume of the total exhaust run, which is a large safety margin. But when I had Michael Start, the diesel guru at Maine Yacht Center, evaluate the exhaust, he concluded the working volume of the waterlock was just about equal to the total volume of the exhaust run. The difference being, apparently, that JFD assumed all of the waterlock’s volume is available to hold exhaust water, and Michael concluded the actual volume available only went up to the waterlock’s inlet from the engine.


The waterlock on my boat. The exhaust hose runs into the top, the hose to the engine runs out from the bottom. To clarify another point, the other non-standard Boréal with a flooded engine had a different waterlock than this, installed well off centerline, and this may have contributed to the problem on that boat

Just to be clear: I don’t entirely understand this waterlock stuff. Also, JFD has never responded substantively to Michael’s assertion.

My thinking about the matter is rather simplistic. I assume any side exhaust installation must be more problematic than a stern exhaust installation, simply because a stern exhaust is really only vulnerable in following seas, while a side exhaust is vulnerable every time a boat is sailing heeled over on top of it.

That is, a side exhaust outlet near a boat’s waterline is submerged underwater roughly half the time you are sailing. Even worse, this submersion in strong windward conditions is very dynamic, with great surges of pressure up the exhaust as the boat plunges through waves with its heeling moment rapidly and suddenly increasing and decreasing. This, I imagine, serves to drive water in pulses of pressure much further up an exhaust line than would be the case when a boat is heeled over in more static conditions. Then, having pushed a fair bit of water well up the exhaust, when you tack over and lift the exhaust outlet out of the water, you effectively swallow all that water into the waterlock, which ideally should be situated (as is the case on the Boréal) on the boat’s centerline and as low as possible. Tack back again, and the process begins anew. If this goes on long enough, back and forth, I assume the waterlock may be overwhelmed, and all the water consumed and swallowed by the exhaust will have nowhere to go but up into the engine.

This sounds logical enough, but the fact remains that Lunacy is the only Boréal with a standard exhaust, out of more than 40 built, that has suffered a flooded engine. And I found it hard to believe I was the first owner ever to sail a boat hard enough to windward to cause the problem.

When I brought the boat to Maine Yacht Center this summer, Brian Harris, the general manager, immediately suggested the problem just might be on the intake side. He had seen situations where boats that had never had a problem suddenly did flood their engines, and it turned out the water had siphoned up the intake after the engine was shut down, continuing to flow though the raw-water pump after it stopped turning, due to a missing vane on the pump’s impeller, or the simple bad luck of having the impeller stop turning at just the right place where water might continue flowing past the vanes. The siphon break, in a case like this, would never have a chance to shoot air into the line, as the flow of water through its loop would never have ceased. For this to occur, Brian explained, the injection point on the intake side, where used raw water from the heat exchanger is sent into the exhaust, needs to be at or near the waterline. And sure enough, this is the case on the Boréal.

Engine waterline

Drawing from Boréal showing waterline level relative to the engine. The raw-water injection point into the exhaust is where you’d expect to be, right near the elbow on the engine

This to me immediately seemed like an attractive answer to the question of what had happened on Lunacy, as it explained why it had never happened before on any other standard-exhaust Boréal. Perhaps it simply had been a case of very bad luck, as JFD first suggested. But ultimately we ruled this out as an explanation. First, we checked the impeller and found no broken vanes, nor did it seem possible for water to move through the raw-water pump when the vanes were not turning. Also, I recalled that JFD had earlier informed me that Lunacy, like other Boréals of recent vintage, had an aft-facing scoop on the engine’s intake hull inlet. This theoretically would make it impossible for water to continue flowing up the intake after the engine and its raw-water pump shut down, as the scoop would immediately create negative pressure and break the water flow.

Therefore, in crafting a final solution to Lunacy’s problem, Michael Start and MYC focused on the exhaust side of the engine. We considered:

–Putting a non-return check valve in the exhaust line so that water could only flow in one direction through it. We did find a valve from Centek large enough to accommodate the exhaust run’s mighty 75mm hose, but the valve itself was correspondingly enormous, and I wasn’t sure where it would fit. Michael, in the end, ruled out this option in any event, as he was afraid the engine would not be able to cope with the back pressure created by the valve. He pointed out also there was always a chance the valve would fail.

–Raising the exhaust loop to deck level. But I ruled this out as this would have entailed repositioning the loop in such a way as to cut off easy access to the engine’s transmission and the shaft seal on the prop shaft.

–Putting a siphon break on the existing exhaust loop. Which was my idea, but was instantly ruled out, as evidently a siphon break for a 75mm line would be much too big to install.

–Installing a simple manual shut-off valve in the exhaust run.

This last solution, which was the one we ultimately adopted, was the very first idea I had when I started pondering the problem in Bermuda, where the engine was dewatered and rehabilitated after our long passage from Porto Santo. The great advantage of a shut-off valve is that it is very simple; the disadvantage is that there is some potential for user error. Indeed, I had some experience with both sides of that equation. On that schooner I mentioned earlier our engine flooded after the skipper forgot to close its exhaust shut-off valve. Later, on my own Alberg 35 Crazy Horse, I once forgot to open the exhaust shut-off valve I had installed before starting the engine and so instantly blew up the muffler.

To prevent at least the latter of these stupid mistakes Michael installed a neutral safety switch on Lunacy’s exhaust shut-off valve, so that the engine cannot start unless the valve is open.

Valve open

Lunacy‘s exhaust shut-off valve open, with a nifty retaining pin to keep it open. The valve is immediately accessible, just inside the engine compartment, immediately under the solid aluminum raised loop, which is not visible here. You can see the safety contact switch, which is connected to the engine’s ignition, just left of the valve handle. The black magic-marker line on the aluminum tube to the right (which is a cockpit drain) shows where the static waterline is

Valve closed

Valve closed. It was, unfortunately, not possible to get a valve this big in Marelon or a similar non-metallic substance, so we had to use bronze

It is as you can see a very mighty valve, and I feel like a person of consequence every time I open and close it, not unlike Master Blaster in my favorite Mad Max movie, Beyond Thunderdome, who used to impose power embargoes on Barter Town by turning on and off great valves in the town’s subterranean methane plant (see the image at the top of this post).

Since I do not know absolutely for certain whether my engine was flooded via the intake or the exhaust, I do take the precaution of closing the valves on both sides after I shut down the engine.

Since installing the valve, I have received more pertinent information and opinions:

–It turns out all of the inlet and outlet scoops on Lunacy’s hull have fallen off. These were simply glued on with some sort of silicone adhesive, which obviously was not strong enough for the job. I have no way of knowing when they fell off, so there may have been no aft-facing scoop on the intake inlet when the engine flooded. (In case you’re wondering, I elected to just leave the scoops off and have not replaced them.)

–Nigel Calder had a chance to inspect Lunacy’s engine and exhaust at the show in Annapolis and he told me he feels the water probably came up the exhaust, though he does agree with JFD that the raised loop in the exhaust run should be high enough to keep this from happening. He does not, however, think it possible for water to have come in through the raw-water pump, as Brian hypothesized.

–My pal Jeff Bolster, who owns a Valiant 40 with a side exhaust, has advised me he installed an external flapper on his exhaust outlet. These are often seen on power boats, hinged at the top so that gravity causes them to cover the outlet when nothing is flowing out of it. Jeff installed his on the forward side of his exhaust outlet, so that it covers the outlet when the boat is moving forward through the water. This seems like a smart idea, though I am not certain I would want it to be the only solution to my problem.

–Boréal has advised me they have concluded putting a check valve in the exhaust run is their preferred solution, though they are still checking with their engine manufacturers to see if back pressure might be a problem. They have offered to reimburse me the money I spent in Bermuda dewatering the engine and getting it running again, plus will give me the cost of a check valve install, once they determine what this is and whether such an install is technically feasible.

For those neophytes who have never had to deal with a flooded engine, I would also like to offer the following tips:

1. Don’t panic! This is as not nearly as disastrous as it sounds. If the problem is handled properly your engine will survive and continue functioning as if nothing ever happened to it.

2. It is best to figure out if the engine has water in it before you try to start it. The tip-off is the oil level. If the engine’s oil level is way high, this is because there is water in there too. The water in some cases will have mixed with the oil, and the oil will look very milky, or it won’t have mixed, in which case the oil will appear normal. In my case aboard Lunacy, I ignored this warning (remember, I was in denial mode), but I was also very lucky. I did no damage to the engine in trying to start it (repeatedly, as it happened). In some cases, however, you can do terrible damage if the pistons have room to move a bit before slamming into the water.

3. To fix the problem you need first to get the water out of the engine. On an older, smaller engine you need only open the decompression lever and turn the engine by hand with a flywheel lever to pump the water out. On newer, larger engines, which tend not to have decompression levers, you’ll need to remove the injectors before turning the engine, by hand or with the starter. Or you can try the trick Nigel Calder urged on me, slipping skinny coins under the exhaust valve rocker arms (see previous post).

4. Once the water is out of the engine, you need to change the oil many times, running the engine at very short intervals, just a couple of minutes, between each oil change. I reckon three oil changes is the minimum number. Five is better. If you’re not in a position to do this immediately after getting the water out of the engine, just leave the water in until you are. This is what we did on Lunacy, as we didn’t have enough engine oil for multiple oil changes when we discovered the problem. You’re better off with the engine full of water, rather than wet inside and full of air, which will quickly lead to major corrosion. In our case we left the water in Lunacy’s engine for about two weeks before removing it, and the engine suffered no ill effects.

SURPRISE ENDING: In spite of her famous flooded-engine problem, it’s just been announced that Lunacy’s appearance at Annapolis garnered the Boréal 47 two Boat of the Year awards from Cruising World magazine, one for best boat overall and one for best midsize cruiser. Very cool! Meanwhile, in SAIL’s Best Boats competition, ironically, the boat won nothing. I did not participate in the judging for the relevant category (Best Cruising Boat 40-50 Feet), but the moment I saw the new Jeanneau Sun Odyssey 440 (the boat that did win the category) while cruising the show, I knew it would be hard to beat.

Lunacy quarter shot

A very nice quarter shot of Lunacy sailing during her CW test. Photo by Jon Whittle

I can actually take a bit of credit here, beyond just getting the boat to Annapolis in the first place. Lunacy was not originally on CW’s list of boats to check out, but I sent an e-mail to remind them of her existence. Also, on the day of Lunacy’s test it was blowing 30 and the CW crew (very considerately, I must say) called to ask what I thought about them sailing her in such conditions. I told them the boat wouldn’t mind in the least, though I was also secretly hoping the two JFs would remember to close the exhaust valve, just in case.

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9 Responses
  1. COYOTE boreal 44

    To take out the water from the oil of the engine, a Volvo mechanic in Tréguier told me to change the oil once, and after to run the engine with the motor top oil plug open. When the oil is very hot, the water will evaporate, and after one hour the oil is clean.
    As to the question if the engine will be damaged, the mechanic said Volvo engines “have seen it all and can get through anything!”

  2. Max

    I like the story and the idea of valving the exhaust, but I’ve seen and repaired substantial corrosion of aluminum plating under bronze plumbing. As the metal condenses water on its outer surface, the drips contain copper sulfates which will bore right through the aluminum. I’d recommend painting the bronze or putting a catchment pan of some sort under.

  3. Damon

    To take out the water from the oil of the engine, a Volvo mechanic in Tréguier told me to change the oil once, and after to run the engine with the motor top oil plug open. When the oil is very hot, the water will evaporate, and after one hour the oil is clean.”

    The water may evaporate but the salt remains behind. I’d do at least one more oil change.

  4. Nick Kats

    Never had this problem but discussed with my mechanic. He said get a squeezy type foam ball, & attach to it a colourful rope. When offshore in building seas, stuff the ball into the exhaust outlet, & tie the rope to the stern pulpit as a reminder. Its the equivalent of your shutoff valve.

  5. Odd Arne Lande Lande

    Thank you for an interesting article on a grim topic, this certainly is and may have a tragic outcome at worst.
    It’s an in-depth review of prospects and we get an insight into something one fortunately rarely hears about, at the same time it scares that it can happen as a “bad luck”. Is this the price we have to pay for not having dry exhaust?
    Your references to professionals reinforce the article and the theories can certainly be truthful.
    I am thinking of Brian Harris who has a theory that the impeller stops in the wrong place so the water continues to flow. Theoretically this should not happen with fresh impeller leaves, but practice is different. Sometimes the diesel engine’s high compression at stop will cause the engine to reverse. One of the leaves can then change direction and there will be a larger gap between the inlet and the outlet of the pump. On simpler constructed water pumps I see the chance for this to happen, but on our Nanni engines I don´t think it is a problem.
    Then it’s interesting what Michael Start tells about the practical volume of the water lock. In that case, it gives fewer margins than intended and this can be of great importance. The foam ball on a rope that Nick Kats up in the comments suggest is a low cost solution, newer heard about this before.
    Very respectable that you figure out what to do if the accident is there, not many people know anything about this. A print of this in the owner’s manual can be a lifesaver☺

  6. Richard

    I’ve never been a fan of using check valves for a siphon break. On the boats that I build I use a small line that starts at the highest part of the vented loop and exhausts into a cockpit drain visible in the cockpit. A small ball valve used to set the flow rate is a useful refinement. Whenever the engine is running there should be a small trickle of water visible. If it stops you’ve lost your cooling system and its time for trouble shooting!

    And yes, every sailboat should have a means of completely closing the exhaust line during heavy going, regardless of whether the exhaust is through the transom or the side.

  7. McCubbin Neil

    although the msiphon breaker was not the problem here, it often is. We have flooded twice due to siphon valves encrusted with salt. We now have a 1/2 » check Val e with a hole in the disc that flows continually and visibly

  8. Robert J. Poole

    “Mutual Fun” Prout 37
    I would be upset if my engine was flooded on a new boat. Especially since you spent over half a loaf. My experience was one of worry. !I bought a new Prout 37 in ’96 (from Tim’s dad) and by ’98 planed to sail her to Bermuda from NJ.
    My engine was at or above the flattation line with a direct exhaust out the back. I could just see a following sea rolling underneath the stern and up the pipe. The manufacturer said no problem, but just in case, I installed a Vetus back flow preventor in the exhaust. And, I had no problem!

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