Staying single, or having twins?

Although the newspapers are full of financial doom and gloom, apparently Nordhavn is still selling boats at a good pace. Oft-times when they sell one of the larger boats (N64, N68 or N76) I get an email or phone call from the buyer seeking advice on outfitting their boat. Just in the past couple of weeks, I’ve spoken several times with two different N68 buyers and an N76 buyer. My friend David, who also owns an N68, had another N68 buyer along on a major passage up the east coast this week.


These calls are always great fun. There are few things more fun than talking about boats, and being able to do so, while it is someone else’s money being spent, makes it even better. I always try to add value, but am not always sure that I do. Generally speaking, there are no “right answers” on these topics. The best I can ever do is to help someone understand the pros and cons of different options.


For instance, I”ve swapped a few emails and phone calls this week with one N68 owner struggling through the decision of twin engines versus single engines. This is a topic where I personally went with twin engines, and would do so again without hestitation, but usually say that a single engine makes more sense.


By comparison to twins, a single engine:


– Is cheaper to buy

– Is cheaper to operate

– Is easier to maintain (half the oil changes!)

– And, uses half the space


I doubt anyone can provide any statistics showing that a twin engine boat is more reliable than a single engine boat. Most of the commercial fishing boats, even those running harsh environments like the Bering Sea, are single engine boats. I do not know the statistics, but I’d but that your chances of a properly maintained and fueled diesel engine failing, are right up there with winning a million dollar lottery. I’ve never won a lottery, and don’t know anyone who has won a lottery.


Plus, Nordhavn doesn’t REALLY make a single engine boat. Virtually all Nordhavns come with a “wing engine”; a small emergency backup (“get home”) engine which turns an independent small feathering prop at the back of the boat. When Roberta and I were crossing the Bay of Lyon, off Spain, a few years back, in our single engine Nordhavn 62, in heavy squalls, and the main engine failed (a fuel problem), I started the wing engine, and finished the passage without incident.


So.. then, why do I, and in fact, MOST owners of larger personal vessels opt for twin engines: I don’t really know. I suspect there are two reasons. 1) A perception of greater safety and reliability (which I contend really isn’t there, especially given that virtually all single engine Nordhavns have a backup wing engine). And, 2) Added maneuverability. Essentially all of the larger Nordhavns have both bow and stern thrusters, so this is not really an issue, although it certainly helps to have the twin engines, and should the thrusters ever fail, it is nice to know that the twins are there to help. Personally, I would have a heck of a time bringing a large single engine boat into a marina with a single engine and no thrusters. Actually I’ve done it a few times with my N62, and it was not easy.


Before leaving this topic, I should talk for a moment about why diesel engines do fail. The #1 issue is fuel. If you give a diesel engine dirty fuel, or have a filter too clogged to allow fuel to flow, it is going to quit. I have seen many Nordhavn owners, over the years, who set their valves incorrectly, such that they were sucking fuel from a tank that has gone dry. In most cases the boat had a thousand gallons of fuel on board, but they were “pulling from the wrong tank” or “forgot to transfer fuel.” On Sans Souci, we have a very rigid set of rules for how we manage fuel, and work the fuel valves, that has worked well for us. My way is by no means the best or only way .. there are lots of ways to skin this cat. The only important thing is that you have a plan, and stick to it.


The second problem is less common, but is the one that concerns me most: Propeller damage. For the boat to move, the entire drive train has to function. If an engine quits, and it isn’t fuel related, there’s a good chance you’ve wrapped a net around the prop. This happened to a single engine N62 we were crossing the Atlantic with. They had to dive the boat in rough seas, but couldn’t get the net cut off. Ultimately, they ran for days to the Azores on the wing engine. I do not know if there is a difference in likelihood to lose both props to a net, between a twin engine boat, and a single engine boat with a wing engine. Were I to guess, I’d think the single engine boat may be better off, because the wing engine prop should not ever wrap a net, because when not in use the prop is neither spinning, nor open.


So .. all this said, why do I personally prefer twin engines?


Three reasons: tight quarters maneuverability, maintainability and redundancy. I like the idea of having two engines that are exact copies of each other. It allows me to scavenge one for parts for the other, if I absolutely had to. Whereas with a main engine and a wing engine, I have two completely different engines to stock parts for. Also, by having twins, I have two engines, either of which can move the boat at full speed. On the passage I noted earlier where I had to run for a day, on my N62, across the Bay of Lyon, on my wing engine, we had to run at 3.5 knots. I really didn’t like being stuck in squalls running that slow. Also, whereas my boat gets MORE efficient running single engine, the wing engines are less efficient. To put this into english, my range is longer if I run single engine, whereas the range is shrunk on a wing engine. The reason is that feathering props are not particularly efficient. So.. if I am 1,000 miles from shore, in the middle of a passage to Hawaii, and lose the main engine – the wing engine is not going to get me to shore. It will keep me moving long enough for the coast guard to send fuel, but I doubt I will reach Hawaii.


As I said, there are no right (or easy) answers to these questions…


-Ken W

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