If you punched a hole in the fuel tank of a 50-plus-foot sportfisherman, the diesel would gush out slower than the rate at which the engines devour the fuel, says one marine industry veteran.
It’s no secret. Boatbuilders, engine manufacturers — and boaters themselves — know powerboats consume eyebrow raising amounts of fuel, making them among the least efficient forms of travel. That’s the price we pay. “Only the helicopter may be worse,” says naval architect Lou Codega. “Water is dense, and there’s only so much you can do to move it out of the way.”
Codega outlined some effective strategies to improve mileage and cut down on fuel expenses at a 2007 boatbuilding conference. Build lighter and slower boats, scale back accommodations, and use the latest propulsion technologies. That was Codega’s message.
“Hear, hear,” his colleagues said after the lecture, titled “Moderate Speed Powerboats, Can Less be More?” They praised his philosophy, shook his hand firmly and patted him on the back.
But that was the extent of their response. Virtually nothing changed.
A year later, companies were still building the same wide, commodious planing hulls, weighed down with berths, heads, galleys, gensets, triple spreader outriggers and a gazillion horsepower.
But there are signs things are changing. With fuel prices on the rise again and the economy still slumping, some boatbuilders and designers are realizing they must embrace a different attitude, one that stresses more thoughtful engineering and de-emphasizes speed and horsepower.
“I guess I am in the enviable position of getting to say, ‘I told you so,’ ” says Codega, who for 20 years has been turning out proven designs for the likes of Regulator, Carolina Classic, Hines-Farley and Mirage Manufacturing (Great Harbour trawlers). “Now [changing] is a problem. It’s easier to do this stuff when times are good.”
Will boats become more efficient? Will the public accept or even ask for those changes once the economy turns around? In other words, will it be business as usual or the start of something new? Ken Fickett believes change will prevail.
“The days of the stylists designing boats are over,” says Fickett, owner of Mirage Manufacturing, which builds both trawlers and open fishing boats. “I don’t think we can go back to where we were. We need to pay a lot more attention to the engineering that goes into a boat. As we come out of the recession, it’ll be the guys who have done their homework who will rise to the top.”
Even if companies begin to build more fuel efficient boats, there’s no guarantee that consumers will be interested, says Michael Peters, founder and president of Michael Peters Yacht Design in Sarasota, Fla. He believes Americans will be hard-pressed to give up their 900-hp, 60-knot vessels.
“These $4 and $5 a gallon [fuel] prices will have to hit us a third and fourth time,” he predicts. “Until then, I don’t think people will change their boating habits or boat companies will turn the corner.”
Case in point is a boat Peters designed in the mid-1980s — a 48-foot ultralight displacement boat with a beam of just 11 feet and a displacement of 14,000pounds. A pair of 145-hp diesels pushes the boat to 26 knots. “One was built — that was it,” he says. Peters also believes consumers will be unwilling to accept a boat with Spartan accommodations in the interests of lightening the load and burning less fuel. “To build a lighter, narrower boat you have to give up a hell of a lot of boat,” says Peters, who has designed for Chris-Craft, Cabo and Regal, as well as many custom powerboats.
Unlike Peters, Fickett believes in the if-you-build-it-they-will-come theory, especially given today’s economic and environmental climates. He’s working on a lightweight 40- to 45-foot dayboat that will get an estimated 2 nautical miles per gallon with a pair of 300-hp Volvo Penta IPS pod drives. Codega is designing the vessel.
“We’re going to leave a lot on the beach,” says Codega, referring to options and amenities. “It’ll be fully cored, long and narrow, but it will be enclosed — sort of like an enclosed express boat.”
To combat their inherent inefficiency, powerboats must be built lighter, which means more boats with cored construction rather than solid fiberglass and wood structures, according to designers and builders. In a number of applications, new, more efficient propulsion technologies, such as IPS and Cummins MerCruiser Diesel’s Zeus, can be used instead of conventional inboards, though they increase initial cost. The boats must become narrower, not only to cut down on weight but also to allow them to run through the water more efficiently.
All of these elements went into the design, engineering and building of the express boats from mJmYachts, which are known for their efficiency. “You’ve got to think it through,” says Doug Zurn, who designed the company’s 34z and new 40z. “You can’t just throw stuff in a fiberglass shell and hope for the best.”
Zurn says 2,000 hours of engineering went into the 40z (the z is for Zurn). The entire hull and deck are cored, impregnated with epoxy resin in a vacuum-bagging process. Both boats have a waterline-length to waterline-beam ratio of about 3.5 to 1, relatively narrow for an express cruiser. The 40z, with twinIPS500s, gets about 1.5 nmpg at 25 knots. The 34z,with a single 380-hp Yanmar diesel and conventional prop and shaft, gets 2 nmpg at the same speed. In the world of boats, that’s pretty efficient, given the speed. Slow it down more, and things only get better.
Twenty-five knots is fast to some boaters and slow to others. No matter what the speed, you can save fuel by slowing down and finding the boat/engine’s most economical rpm setting — the so-called “sweet spot.”
Capt. Stefan Czuplak skippers a 105-foot Azimut with twin 2,000-hp MTU Detroit diesels. At 20.5 knots, the Azimut burns 159 gallons per hour; at 10 knots it burns 26 gph. “I can burn 4,000 gallons and go 500 miles or go 1,300 miles and burn the same amount of fuel,” going slower, says Czuplak.
The Down East semi-displacement Duffy 31 with a single 380-hp Yanmar diesel consumes 10 gph at 20 knots, or travels 2 nmpg. Back her down to 12 knots, and she burns 3 gph, or 4 nmpg. That’s pretty good mileage for a recreational powerboat.
In contrast, a 33-foot twin 300-hp gasoline inboard express cruiser burns about 30 gph at 29 knots and is lucky to get 1 nmpg. Push that boat to 34 knots, and the burn rate can more than double. A big center console with triple 300-hp 4-strokes traveling at 45knots consumes more than 100 gph for just more than 0.5 nmpg. You pay a price for speed.
In a recent sea trial, a Viking 50 Convertible at a comfortable cruise of 30 knots consumed 74 gph with its twin 1,360-hp MAN 12-cylinder common-rail diesels. That equates to 0.4 nmpg and a range of 496 nautical miles on her 1,200-gallon fuel capacity. And keep in mind that these numbers were generated during ideal conditions, says Peter Frederiksen, Viking director of communications.
“This boat was fresh, with a clean bottom, finely tuned custom propellers, and a reasonable payload of gear, fuel, water, passengers,” he says. “A boat’s speed is connected at the hip not only to horsepower and weight, but also to the conditions, pertaining to the bottom, the depth of water, sea state, fuel quality and various other factors. Also, many boats are improperly propped or are using propellers that are out of pitch, and these factors are extremely detrimental to fuel efficiency.”
Many boat owners — especially those with smaller boats — would do well to put their boats on extreme diets and not carry everything they own when simply out for a day of fishing or cruising.
Operating a boat properly makes a difference, too, says Codega. “I see so many boats running with their bows too far down,” he says. “Pay attention to trim angle. When running in calm water, get as much of the boat out of the water as possible. Bring [the bow] up till it porpoises, and then bring it back down a bit.”
Editor's Note: Time to Throttle Back, part 2, gives more advice on saving fuel.
Chris Landry is a staff writer for Soundings Magazine. The entire article originally appeared in the December 2009 issue of Soundings.