One NM Per Gallon, Fast or Slow

I've been thinking recently about the design spiral and the elements that figure into the selection process. So many considerations come to mind that have nothing to do with single versus twin engines, which ultimately is not very important to me, nor should it be to you. And while I admit dreaming of my next cruising boat is not machinery driven, I wonder how I will come out on the miles-per-gallon equation this time.

When we owned Growler, our 36-foot Zimmerman Marine cruiser, it averaged one nautical miles per gallon of diesel. Sure you could tweak this number one way or the other, but running at speed for general cruising was one mile per gallon. Slow down to single digits, of course, brought the mileage way up.  

Growler in Bahamas.JPG

Capt Mike Efford got the same one mile per gallon number on his 65-foot, 90-ton Army T-Boat, Mi-T-Mo. So do friends on their Grand Banks Eastbays. Ditto a friend with his Fleming, as well as another on his 58-foot Nordlund.


Andy Lund of Grand Yachts Northwest, the one-time Grand Banks dealer for the PNW, said he could toggle between his 42 Classic or Eastbay and get the same result: one nm per gallon of diesel. For him it all came down to how he wanted to enjoy the equation. Go fast and get to SE Alaska quickly on his Eastbay, then slow down and smell the roses. Or work up the coast with a bigger, more comfortable boat, as in a  popular and proven Grand Banks Classic. The GB 42 Classic (Heritage in recent times) with naturally aspirated 3208s burns close to 10 gph at 10 knots. The Eastbay with 3126s will burn very close to 20 gph at 20 knots, or close enough to make the argument that you can get there in half the time, but arrive with less accommodations and storage than you will find on a 42 Classic.


I have notes from so many other boats where it really comes down to deciding where one wanted to be in this game. Quick like a rabbit to get there, or poke along with your feet up? Is it the journey or the destination? 

During the PMM Pokie Run we hosted years back, which brought 39 newbie boats and their owners across the Gulf Stream to explore the Bahamas for the first time from West Palm Beach, one boat stood out in terms of performance. Bill Watson and his wife were aboard a Tom Fexas design, a Midnight Lace. This super cool motorboat reeks of style (and Miami Vice) and runs like a PT-boat-inspired thoroughbred. Bill and Barbara would lounge in the morning over coffee and breakfast, as the rest of the Pokie fleet lifted our anchors and headed to the next anchorage or selected marina. The Watsons would take their time leaving, but always got there before us as their cruising speed was significantly higher than any of the other boats. This cruiser burns just 18 gph at 25 knots.

The Midnight Lace Rum Runner stands out despite its 1980's vintage.

The Midnight Lace Rum Runner stands out despite its 1980's vintage.

It was great fun and we all had a laugh over the lightweight modern rocket ship versus heavy, slow trawlers among us.

Chip Shea of Luhrs Marine Group used to talk about this at his company's rendezvous events, where the fleet of Silverton motoryachts mixed among the various versions of Mainship trawlers. Some of the older Nantucket Mainships, which are decidedly seven-knot boats, are well loved and cozy in their ability to get there in comfort and economy. The Silverton crowd prefers to blast along and get there right quick, and yet the social difference at the end of the day was hardly noticeable, jewelry aside.

Obviously, some larger fast boats are way out of our power cruising league when it comes to fuel consumption, some beyond comprehension. When I toured a new cruising yacht at the Palm Beach Show, the builder explained that this huge, three-engine motoryacht could run offshore at 35+ knots while burning 165 gph. One could reach Cape Cod well before the rest of the crowd. I put my checkbook away. That doesn't even seem in the realm of responsible boating, in my opinion. I can’t conceive of owning such a monster fuel guzzler, no matter how lovely the interior. Yet I toured a beautiful Spencer 74 sportfishing yacht that burns 230 gph, so my perspective isn't the general opinion.

So as I contemplate our next cruising boat, where does this leave me? The single versus twin debate, and its associated fuel consumption, isn't a deciding factor as much as it is a consequence of our chosen style of cruising. Having owned a fast Hunt Harrier day cruiser, capable of exceeding 40 knots, I am well aware of the benefits of choosing the right weather window and conditions and having a delightful speed run on open water. And my friend Jim Ellis is fond of saying that he always preferred to be in port on his Fleming 55, but for the actual underway experience, he much preferred the agility, comfort, and performance of my PDQ 41 power cat. He couldn't stand its non-traditional look, but loved how this boat could fly while burning so little fuel.

My preference seems to change from day to day as we move from winter into spring. Do I choose the speed and handling of a faster boat to get there sooner, or the comfort of a larger liveaboard platform when we arrive, such as found on any number of DeFevers, Krogens, and Grand Banks? A speedier boat, such as the Ray Hunt-designed Eastbay (or Sabre or Nordic Tug or whatever) won't need stabilizers, but the wider, heavier trawler yachts will definitely be more comfortable for longer stays at the next destination. Which is more important?


At some point, I will have to make an honest appraisal of how we will really use the boat, and what kind of cruising we plan to do. In so many ways, it becomes a common sense discussion once you agree on the mission statement. Growler was a great cruising boat for two, but I felt it too small for living an entire winter in the Keys.


Conversely, a bigger boat, such as the Krogen 48 we looked at, or a DeFever 49, would be ideal for a winter liveaboard, yet way overkill for a summer of weekends on Chesapeake Bay. But adding speed back into the picture with accommodations will also make the difference when deciding to go or not go...yet to enjoy higher speed with comfortable accommodations requires a rather large speedster...and an Eastbay 54 is no casual runabout.


So much to consider.