© Attainable Adventure Cruising Ltd and the authors, all rights are reserved.
Nothing on this website or in direct communications received from us, or in our articles in the media, should be construed to mean or imply that offshore voyaging is anything other than potentially hazardous. Dangers such as, but not limited to, extreme weather, cold, ice, lack of help or assistance, gear failure, grounding, and falling overboard could injure or kill you and wreck your boat. Decisions such as, but not limited to, heading offshore, where you go, and how you equip your boat, are yours and yours alone. The information on this web site is based on what has worked for the authors in the past, but that does not mean it will work for you, or that it is the best, or even a good way for you to do things.
We motorsailed off a nasty lee shore in NZ when I was a kid. A very unpleasant night, with the Bay of Islands in our lee, could have run into the Bay and found shelter but 40 or so knots of an easterly (with heavy rain) would have made this far too dangerous in the days before GPS, and probably still too dangerous even now with GPS and radar.
We kept kicking the prop out of the water (offset to port and quite shallow, L.F.Herreshoff, Mobjack). We had to play the throttle, easing up as we came over the top of a wave and putting on the power during a flat patch. Worked well, but glad the throttle cable didn’t break.
And yes my parents’ boat had its engine fill up with salt water deep in the Southern Ocean on the way to Mururoa Atoll (near Tahiti); she was heavily loaded and in some very nasty weather (mid winter). They now have a very high dry riser and close the valve in bad weather, so it is a very important point.
Must also say I like to have an effective third reef for the same reasons as you; the time you really need it may well be coastal, getting off a close lee shore, with a broken engine, no time to mess with a trysail, and you may need to quickly shake out to a double reef as soon as the wind eases, or if you aren’t making progress.
I am interested in your exhaust system, as I need to replace mine at some point; it is a dry exhaust, with keel cooling.
If it were me, I would stay with your dry exhaust keel cooler system. If I was building a new metal boat from scratch, that is what I would do.
I have a NorthSea exhaust system on my sailboat: A 3.5 inch diameter tube that runs from one side of the boat to the other just behind the engine with the wet exhaust in the center, which pours water in the tube. A wave from the stern can’t affect it. If a wave hits from one side, the exhaust continues out the other side. Two waves, one from either side, would cancel each other. Another advantage is no exhaust smell no matter what wind direction…
This is my inclination, as I already have the exhaust on one side. I would love to see your installation.
A valve in the exhaust is a sure way of keeping the water out, but what are the consequences of forgetting to open in when starting the engine?
Failure to start would be no big deal, but damaging the system would be.
Hi Neil,
I have never tried it, and won’t, but I have been told by an experienced diesel mechanic that the engine probable won’t start and if it does it will quickly stall.
I guess that yes, you could make the mistake of forgetting to open the valve, but turning the engine battery switch off and marking it with a small sign to remind yourself that the exhaust valve is off will go a long way to fix in that. I think the small risk of forgetting is worth taking when measured against the risk of flooding the engine, a very common occurrence in heavy weather, although avoidable with the right exhaust design.
My 46′ sloop has a hefty exhaust outlet shut-off valve mounted beneath the deck in the lazarette. Its purpose is to prevent engine flooding though the exhaust while sailing in following seas as discussed above. New to the boat in 2008 I was also new to auxiliary marine engines and neglected to open this valve during commissioning. The engine did start and run. After 20 or 30 seconds or so a great burst of exhaust bubbles rose to the surface beside the hull. With nowhere to go, the exhaust gasses had compressing within the volume of the exhaust system until sufficient pressure was reached to deflect the raw water impeller blades, purge the raw water, and vent through the seacock.
Fortunately, the situation was immediately obvious from the cockpit. No component of the raw water or exhaust systems were damaged. I can imagine a different and worse outcome had the seacock also been closed. I can also imagine the same problem going undetected in heavy weather or at night and the engine left to run. How many minutes would it take for the engine to overheat or for the impeller and/or various hoses in the raw water circuit to begin melting? So while in the short term it proved harmless I would not want to empirically test longer term effects.
Great site, by the way.
I imagine that the prop-wash flowing over the rudder must also be a considerable help when steering to windward in these conditions, especially as speed through the water is likely to be very slow.
On our Morgan 382 sloop we attach our ignition key to the 2″ shutoff valve at the exhaust outlet. It takes 5 seconds to open valve and retrieve the key. When engine is shut down the key is put back and the valve is closed. This idea came from an “Old Salt” and works great.
Hi Geoff,
Great idea, we do exactly the same thing when the inlet seacock to the engine is off on our boat.
After an incident of forgetfulness very early in my sailing career, I too hung the keys on the handle of the raw water inlet. I stopped doing it once the habit of ALWAYS inspecting the motor prior to start (oil check, water on, smell for fuel, switch on fuel cock, etc.) became habitual.
In my new exhaust setup, I will have a three-way valve going from the exhaust to a “North Sea”-style transverse exhaust. It may be time to revive this old idea to ensure that the “keep water backing down to the waterlift” valve closing doesn’t bring us to grief one day.
I can testify of the value of an engine in a sailboat having battled hurricane Irene, then a tropical storm where i was near Quebec city but still 50 knots gusting to 60 in a river about 1 mile large… It took 1 hour to do 2 miles with the NE wind perfectly in front of us. I was happy to arrive in the locks, the marina was already suffering damage and the big tugboats were entering the lock to hide from the storm because it was really nasty on the river with 3-4 meters swell starting to enter the port.
To my humble opinion, a modern safe sailboat is really first and foremost a mechanical engine propulsion ship coupled with a complete autonomous sailing system. Both installation should be first quality and capable in any circumstance.
It would be helpful to have a drawing of your recommended exhaust system, and especially how a surge tube could be installed.
Hi Eivind,
I hear you, but the problem is that there are so many different boats and engines that coming up with anything that would work for all, or even most, would be impossible.
That said, if you want a system like ours, Halyard will help you with the design as long as you buy the kit from them.
As to the surge tube, if you just built it like the photo, but sized for your boat, it should work fine, with one caveat: It will add some exhaust back pressure, so it would be wise to check for that both before and after the surge tube is installed and to make sure that the engine manufacture’s spec has not been exceeded.
Thank you for your prompt reply.
I was just thinking about a graphic that showed the critical relationship of height relative to waterline and other references, and I would of course understand that this would have to be adjusted to my own boat.
Very impressed with the quality of your website, although it sometimes feels like sailing will be in survival mode most of the time ?
Hi Eivind,
Hum, not sure my drawing skills, or knowledge of exhaust systems is up to that, but what I can say is that with common mixed gas and water exhaust systems two things are important to stop flooding:
The idea here is that when at sea and well healed said high point should never be below the effective waterline.
Sadly both of these are quite difficult to do and many production boat builders cut corners in this area to maximize accommodations.
On balance, if you think there maybe a problem, I would do as I suggest in the article above.
Clean fuel !!
We to have a polishing system as John described above. But our day tank sits between the main engines and the alu round bilge hull helps keep the fuel cool. I drilled a 3/4 hole on either side of the tank directly above the deepest part, tapped it to accept the proper size plug.
Whenever fuel is transferred from one of the other tanks or directly from an on shore outlet, wait about half an hour or so for any contaminant to settle down and a semi rigid plastic pipe is put down to the deepest part of the tank, which is connected to a shop vac and is able to suck up any water, sludge etc . The plastic pipe is about 1/2 ” and 4 ft long.
The shop vac may not have enough power if a bigger tube is used, depending ofcourse on the length. Usually repeat the procedure every month or so and have not needed to switch over the fuel-filter valve for a number of years. The vac gauge shows well below 6. The reason for a hole on either side of the tank is because of the 6″ x 1″ thick center keel beam running through the tank. After a few liters have been vacuumed out , empty the shop vac into a clear plastic bottle and inspect the contents. The procedure is repeated until all is clear diesel.
Interesting article and very interesting comments as well. Looking at the yanmar engine setup on my bayfield 29 I can’t see a possibility of any water getting up and over the mixing elbow and into the engine. Both the design of the exhaust and the mixing elbow itself was designed to keep water on the exist side of that elbow. Without the boat going way past 90 degrees if not completely over. Hope I never face that situation. There is little risk of water coming in through the stern exhaust port up past the wet muffler hose and muffler and up to the elbow never mind over the top of the elbow and into the exhaust manifold. BUT despite all of that there is a large seacock at the stern exit that could be closed. If waves were breaking against my stern that water getting in my engine was a risk. More likely the bigger danger would be waves filling the cockpit and then If the cockpit drains couldn’t keep up I would be relying on the engine hatch seal to keep the water from flooding the engine room from above. (Which does have two heavy duty latches that keep pressure on the seal but I doubt If the cockpit was full for long it would be completely water tight.
Hi Michael,
Sounds like a good analysis of the issues, and that’s at least half the battle in that most people don’t even think about this stuff before going to sea for the first time.
I think, if it were me, I would run a test by closing the drain seacocks and then filling the cockpit with a hose to see what the water ingress looks like. The point being that once offshore and keeping the sea in a blow, filling the cockpit is a much more common occurrence than many people think, and the smaller the boat, the more commonly it happens, so we need to be sure that there is not going to be a lot of water getting into the boat each time it happens, because that can become a reinforcing downflood cycle, as well as killing the engine.
Perhaps the “diesel induced lift” phenomena could also be called “diesel reduced drag.” The idea being that the first stage of forcing the prop to rotate merely eliminates the drag caused by the prop and it’s supporting structure. There is a natural rpm which the skipper senses is enough for the conditions. It would be interesting to know where this point was in relation to the point where the prop was giving just enough drive to overcome its own drag but no additional drive. They might be the same.
A feathering prop reduces drag but there is still some, and it’s supporting structure (shaft or saildrive) also gives drag so, there might still be a case that overcoming drag is sufficient.
Dehler went to the trouble of implementing a retractable stealth drive in their 30OD*. Perhaps their R&D showed an advantage over the smoothest, feathering, permanent alternative. If I had a 30OD I’d do the experiment:
Of course there will come conditions that stop a OD30’s windward progress even in stealth mode, and deploying the motor will be advantageous. Even so, there is a lot of drag from the rig that the motor may be overcoming (after overcoming its own drag first.) When fully reefed there is a lot of mast that is adding nothing but drag. Maybe the point at which windward progress is restored is merely the point that overcomes this excess rig-drag.
I guess I’m thinking that the more we reduce drag aloft and alow, the later we need to think about starting the engine, and if the drive can be retracted, perhaps the engine-starting point can be significantly delayed. Nonetheless, I have no argument at all with the suggestion that eventually the engine will become essential to safety.
* https://www.youtube.com/watch?v=FMqQM1pvEUM