Choices like engine brand are personal. We didn’t make a Deere vs Lugger decision on our Nordhavn 52—we would have been happy with either. Although the high quality support offered by Lugger clearly is important, the reason why 5263 will have a John Deere main is that we wanted a little bit more power and Lugger didn’t produce one that would fit.
The Nordhavn 52 is a longer, heavier version of the Nordhavn 47, and we had heard from many Nordhavn 47 owners “wonderful boat, but I wish it was just a little faster.” This is not a universal sentiment. Many hold the opposite view and argue that the boats would be better with less power. Nonetheless, many owners I respect wanted more speed, and this influenced our decision.
The arguments against higher horsepower include greater fuel consumption, increased engine weight and the risk of engine underload. What folks sometimes don’t understand is that a 265 HP engine operating at 150 HP will consume very nearly the same fuel as a similarly designed engine rated at 165 HP also operating at 150 HP. Fuel consumption is driven by the horsepower produced, rather than the engine’s rated horsepower. And in this case, engine weight is not a factor. The Lugger 1066T.2 that is standard with the Nordhavn 47 and 52 is a marinized John Deere 6068—the same engine series that we are installing.
Some folks agree that a higher horsepower engine occasionally would be nice for increased speed, but argue that the additional horsepower rarely would be used. As a consequent, the main would spend much of its life very lightly loaded. There is no question that engines need to be run at the designed operating temperature to reach full life. My experience with 4,000 hours on my current Cummins engines is that engines can be operated at very low HP outputs while still maintaining proper operating temperature. This, however, is a hotly debated topic. Personally, given the choice of 1) not having the power to achieve a speed-length ratio of at least 1.34 or 2) being able to achieve 1.34 but with the engines often operated at a lighter load, I prefer the second camp. And, I’ve seen more engines damaged by overload than under. But I don’t discount the concern entirely. Boating is full of compromises and tough decisions.
In thinking through whether the 52 needed more horsepower, we calculated horsepower per thousand pounds across the Nordhavn fleet:
• N40: 3.30 (50,000 lb @ 165 HP)
• N43: 2.75 (60,000 lb @ 165 HP)
• N43: 1.75 (60,000 lb @ 105 HP original engine)
• N46: 1.75 (60,000 lb FD @ 105 HP)
• N47: 1.94 (85,000 lb FD @ 165 HP)
• N50: 3.75 (80,000 lb FD @ 300 HP)
• N55: 2.66 (124,500 lb FD @ 330 HP)
• N57: 2.66 (122,000 lb FD @ 325 HP)
• N62: 2.19 (155,000 lb FD @ 340 HP)
Note: Weights are based on published specs at the time we did the calculations. Some are full load (FD), others are ambiguous. It’s rare, however, that any boat weighs exactly what a manufacturer claims.
With the extended cockpit and flybridge, not to mention all the equipment we planned to install, the 52 would be a heavier boat that the 47. If we assume it would weigh 100,000 lbs fully loaded, the standard 165 HP would be make it the lowest powered boat in the fleet with a ratio of only 1.65 HP/1000 lbs. I’ve been on the original 43 with only 105 HP, and did not want to have less power to weight.
Lugger doesn’t make a more powerful engine that will fit, so in this case, the decision was not really based on brand as much as output requirements. We went with a keel-cooled John Deere 265HP 6068AFM75. This provides 2.65 HP/1000 lbs, which is just about identical to the Nordhavn 55 and 57, although still less than the 50. As an added bonus, the 6068AFM75 is 14% more efficient at rated output, is more efficient across the operating range, and is closer to a continuous duty engine than the Lugger 1066T.2.
Rusty, from my perspective the 52 build rate seems fairly typical although we have to admit we would love to see the boat done. Ignoring are eagerness to see it, the completion rate has been fairly typical. The hull was laid up in February and I think it’ll be done at the yard in about 4 weeks. Roughly 9 months seems about right.
You were asking about 52 sales? I don’t think that PAE discloses the details but, generally, what I’m seeing is that the big boats continue to be sold whereas sales of the smaller members of the fleet have been dramatically slowed by the economic downturn.
Hopefully we’ll see 5263 in Seattle in November.
James Hamilton
jrh@mvdirona.com
It seems like it has taken a longer time for Nordhavn to roll out the N52 than some of their other models. I thought the N60 was announced at roughly the same time and I think several of those have already been delivered. Do you have a sense of how many other N52’s are in production at this point. I would think it would be a very popular model.
Thanks ….
I think there is sufficient space and I suspect you could get a sea chest in a 52 if you wanted it badly and mentioned it up front. There have been some service issues on sea chests on the smaller boats. For example, collecting air at the top. If you want it badly and pushed for it early, I suspect you would get it. I personally would have preferred to have one.
James Hamilton
jrh@mvdirona.com
Fair enough. It’s really too bad there isn’t the chance for a sea chest as on the larger boats. Eliminating all those through hulls would add to simplicity and peace of mind. My limited research revealed they felt insufficient room. I am sure you explored that with them and found likewise. Looking forward to your reports on delivery and commissioning. Thanks for the blog and being so generous with your time sharing the details. -af-
Its a keel cooled, dry stack approach. There are upsides and downsides to both keel cooled and heat exchanger designs. PAE strongly prefers keel cooled for the 47/52 but they use heat exchangers on the bigger boats. I can show you ugly failure modes either way so don’t have a strong preference myself. I might slightly prefer keel cooled just to avoid the large through hull required by heat exchanger engines but, by the time you get all the through hulls required by A/C, generators, wing engines, etc. I’m not sure this advantage is really there. I’m fine either way.
James Hamilton
jrh@mvdirona.com
James:
Does this mean wet exhaust or were you able to keep a dry stack? If so, did that influence your decision at all (i.e. did/do you prefer either?)? cheers, -af-
The increased efficiency comes primarily from the use of an after-cooler and high pressure common rail injection. Both are turbo charged. After turbo charging, air inlet temperatures can rise to well over 350F. Cooling the inlet air with an after-cooler is near free hp. Why wouldn’t lugger do it? There is a strong argument for simplicity in ocean crossing boats. The more complexity the possibility for failure.
The same is true of computer controlled, high-pressure, common-rail injection systems. Much more precise over much wider operating ranges but they are more complex than old mechanical systems. Many folks would rather have a less efficient mechanical injection systems in an ocean crossing boat.
The efficiency doesn’t come without cost but it looks like a good trade-off to me.
James Hamilton
jrh@mvdirona.com
James –
I find it interesting that the Lugger and John Deere models of the same engine have such significant differences in their performance specs. Does the higher output/efficiency you receive on the Deere come with any tradeoffs such as a shorter life? What has Deere done to result in the improvements?
Thanks …
Your argument that at higher speed to length ratios, waterline length becomes the dominant factor makes complete sense. At lower S/L ratios, I would think displacement would be the dominant factor. 7 knots may be fast enough for the 43 that waterline length (or lack of it) is the dominant factor.
On the data quality, it may indeed be suspect but they do claim two passes in in each direction 180 degrees opposed measured with GPS. The reason the top speed is so low compared with your experience with other 43s may be that the 43 has had different HP engines over the years. The first was 105hp, I think there was 143 hp offered as well, and it now has the same 165hp engine that is used in the 47 and the 52. This data is from the earliest configuration that appears to be fairly seriously under-powered.
I’m looking forward to seeing how the 52 does. Just another few months.
I would have thought the N43 would do a little better as well, but clearly S/L is working against the little boat.
At 7 knots, the N43’s 38 foot waterline puts its S/L at 1.14. The N55’s 50 foot waterline puts its S/L at 0.98. The amount of power required increases nonlinearly with respect to S/L. The N43 is a bit further up that steep curve.
But that table also showed that the N43 could barely exceed 7 knots at full power. N40’s can hit around 8.5 knots, so perhaps that boat was working against a current during the test or had a really bad bottom. The data looks rotten.
That said, I have seen a few data sets that said the N55 can equal the mileage of an N47 in some speed ranges, which suggests that S/L can overcome weight differences to some degree.
Interesting John. That observation draws the Power and Motor Yacht data into question. I totally agree that waterline length is a wonderful thing but there is no way that a 55 should be getting the same mileage as a 43 at 7 kts. They are similarly designed boats so I would expect displacement would be the dominate factor until S/L ratios are well over 1. And, I wouldn’t think that 7 kts was fast enough to see that effect.
That one is hard to explain — I’m looking forward to seeing how our 52 does at that 7kts. It looks like it may be ready to ship at the end of October or early November to get commissioned in Seattle.
James Hamilton
jrh@mvdirona.com
Interesting to note that the N43 at 7 knots gets exactly the same mileage as my N55, which weighs more than twice as much. Waterline length is a wonderful thing.
This also confirms that the weight of a displacement boat is not a significant factor in efficiency, at least in fairly flat water.
John Marshall
Good hearing from you John.
What pushed us to opt for more power in our 52 is a combination of factors: 1) the table in the original article where the standard 163 hp engine would put the 52 as one of the lowest powered boats in the Nordhavn fleet, 2) from reading the Power and Motoryacht article on the Nordhavn43 where they found it couldn’t achieve a speed to length ratio of 1.2, and 5) several 47 owners have said they would never need more speed ocean cross but there are rare times when coastal cruising that they wish they could trade efficiency for speed, spend a bit more, and run a ½ or full knot faster
The Power and Motor Yacht article testing the original 43 has since been changed or replaced on the web but the original one included this table: //mvdirona.com/blog/content/binary/PowerAndMotoryacht43Specs.jpg. From this table we can see that the original N43 could only achieve a speed to length ratio of 1.18 or 7.3 kts wide open. Incidentally the 43 now uses the same engine as the 47 and the 52 so this comparison no longer applies. This table was particularly influential in our thinking in that we wanted to be able to achieve S/L ratios of at 1.3 to 1.4 even though it’s clear we wouldn’t use the higher speeds often.
In our current boat, our normal cruising speed is 7.2 to 7.5 knots and we burn about 2.2 gallons/hour at this speed. We’re comfortable at this speed and so is the boat. But, we had it as a hard requirement that the new boat can’t be slower, we would like it a knot faster, we didn’t want to have to run wide open, and we would really like to achieve a speed to length ratio of 1.34 which is 9.3 kts.
I know you are right that we’ll spend much of our time at a speed/length of 1.1 (7.6kts) but we wanted the higher speeds for occasional coastal cruising use.
James Hamilton
jrh@mvdirona.com
Biff, you are correct, a controllable pitch propeller is an excellent choice but its really an independent point from how much power we want in the new boat. The problem a controllable pitch propeller helps solve is that a fixed pitch prop is only the correct pitch for a very narrow speed and load range. Fixed pitch propellers are a compromise whereas a variable pitch can be tuned for the current load and speed. Variable pitch contribute greatly to increased efficiency and they help ensure the engine is properly loaded for all operating conditions. Variable pitch props are very common in commercial aviation and in commercial marine applications. Again, increased efficiency.
The downside of variable pitch is they are both complex and expensive. The Nordhavn 56 Motor Sailor is equipped with a variable pitch prop so we’ll be able to learn about them and there application to smaller boats. I suspect we’ll learn they are a clear win and they will get more common. If fuel prices climb enough, we may end up going the same route.
We elected to go with a simpler fixed blade prop but did go with a more efficient 5 blade design rather than the standard 4 blade.
James Hamilton
jrh@mvdirona.com
James,
Interesting arguments… I’ve been arguing this case from the other side, believing that a smaller engine run harder is the way to go. I’ve got a 6081AFM75 in my N55 (which by the way, makes 330 hp not 300 as you list above, and we weight a bit over 130,000 pounds), but rarely use it above 40% power, and generally cruise at 25% power, which is lower than the engine likes. I have to blow out the engine each day with some 80% or higher runs to keep it clean. If I could economically trade it for the 6068AFM75 (which I think is the sweetest engine that JD makes, by the way), and drop the HP from 330 down to 265, I’d do it in a heartbeat. At 25% power, I burn 4gph and make 7 knots. At 60% power, I burn 9.6gph and go about 8.5 knots. While the engine is happier up there, my fuel mileage is awful. Even worse, the boat simply feels better and has a kindlier, softer motion at 7 knots than at 8.5. Plus its far quieter at the low RPM. i’ve put about 10,000nm on my boat, and have experimented at cruising at all kinds of speeds, but have concluded after all that, that the N55 is perfect in the 6.8 to 7.2 knot range, at least for us. (In fairness, I know of other N55 owners who love running at 8.5 knots, so its a personal preference thing).
Not sure where the N52 fits into this, but I suspect the N55 and N52 will be pretty similar, given the N55 is just a "scaled up" N47. Looking forward to meeting you on the water once you guys are out cruising on your new N52.
John Marshall
Have you consider a Controllable Pitch Propeller? The pitch can be adjusted as needed in order fully load the engine at nearly any rpm. You would also be able to eliminate the reversing gear – a smooth transition from ahead to astern simply by reversing the pitch. The CPP is widely used in Europe and nearly universally used in the Scandinavian countries.