The Way Forward: Sea Ray Goes Electric

Boat Tests


  • Sea Ray
  • 2008
  • Other...
  • 24'10"
  • 8'6"
  • 3'4"
  • 5,593 lbs.
  • 1/260-bhp MerCruiser 5.0L MPI Bravo III gasoline stern drive
  • 75 gal.
  • 20 gal.


Standard Equipment: Taylor Made curved-glass windshield
80-watt Sharp solar array
VDO instrumentation
Quicksilver throttle/shift
Raymarine ST60 depth/speed indicator
4/Odyssey PC2250 Group 31 AGM deep-cycle batteries (hybrid bank) and 2/Group 27 Stowaway batteries (12v system)
Bennett trim tabs


1/250-mhp Steyr MO256H45 diesel inboard w/7-kW 48vDC motor and 5-kW 48vDC generator

Bravo III/2/2/1

The Numbers

The first thing I noticed about Sea Ray's so-called "Green Boat" was her conventional appearance. Sure, there was something atop the bimini—a Sharp solar collector—but the gizmo was inconspicuous. And the hull sides were a perky willow green, with racy, black waterline stripes proclaiming: HYBRID. But otherwise, our test boat du jour looked like a regular ol' off-the-shelf 240 Sundancer.

The second thing I noticed vaguely hinted that this 240 featured one of the most innovative propulsion systems ever installed by a mainstream manufacturer. While the steering console had the usual Sea Ray stuff—Teleflex wheel, Quicksilver engine control, Carling Technologies toggles—there were mysterious extras as well: a Steyr Control Center LCD panel and a green button next to a black rocker under the wheel, both enigmatically unlabeled.

"This is an iffy project—even if we do decide to go to market it won't be until next year or maybe later," said Sea Ray engineering tech Doug Weyant while lifting the engine-room hatch at the rear of the cockpit. Weyant had been the principal creator of the Green Boat during the previous months, integrating into a standard production envelope various environmentally friendly technologies, chief among them the single 250-mhp Steyr MO256H45 Steyr Motors Hybrid diesel (see "Austrian Ingenuity," page 54) I was eyeballing in the engine bay. It was linked to a MerCruiser Bravo III drive and, according to Weyant, promised all-electric operation at maneuvering speeds.

A couple of ancillaries drew my interest as well. First there was the bank of four Group 31 Odyssey 2250 AGM (pure-lead) batteries, the main electrical storage bank for our Steyr's 48-volt D.C. system. Weyant told me he'd wanted to go with lithium-ion batteries with more storage capacity but ran out of time. The Odysseys were installed in an alcove in the forward firewall and, according to Weyant, had enough capacity to not only reasonably deal with all-electric propulsion but operate the boat's 7,000-Btu air-conditioning system for approximately eight hours, thus keeping the cabin cool for sleeping overnight at anchor.

Then there was the 12-volt system, a seeming redundancy. In addition to the somewhat ponderous Austrian electricals in the engine room, there was a more conventional setup, comprised of two Group 27 Stowaway batteries charged via a traditional engine-mounted alternator. Weyant said that besides energizing lights, instruments, and other house-type equipage, the system could also crank the diesel in case the Odysseys were inadvertently drained. He added that the unlabeled green button I'd noticed on the steering console was for cranking the diesel in this fashion.

Driving Sea Ray's Green Boat was not unlike driving a conventional stern drive, at least at first. In primary-diesel mode, the average top end I recorded was 38.7 mph, somewhat less than I'd expect from the standard 260-hp MerCruiser 5.0L MPI Bravo III package. Maximum fuel burn was 15.7 gph, way less than the aforementioned gasoline package.

Subtle differences began to arise eventually. Primary-diesel acceleration was noticeably robust, thanks to the hybrid's ability to boost torque on the lower end of the rpm register (see the acceleration curve, this story). And remember that black rocker switch on the steering console I mentioned earlier? To toggle from primary-diesel to all-electric mode I had to first shut off the diesel via the ignition key, then hit the rocker to energize the Steyr's electric motor and align it with the Quicksilver engine control.

Subtlety totally disappeared with the advent of the much anticipated all-electric mode. Driving was an absolute hoot! The system silently pushed the 240 along at 4.9 mph while drawing 90 amps from the Odysseys, for a respectable run time of approximately one hour. We topped out at 5.6 mph while drawing 150 amps, for a significantly diminished run time of approximately 25 minutes. These speeds were so close to those I got while idling on primary-diesel power alone that I could hardly tell the difference—except for the absence of smoke, smell, vibration, and engine noise. Moreover, I felt that the maneuvering clout and shifting response while docking at slower speeds were virtually the same as in the diesel mode, although it's worth noting that weather conditions were benign at the time, with virtually no wind or current.

The price? Sea Ray hasn't put one on the Green Boat yet. In fact, at presstime, the company was still gauging interest from dealers, employees, and journalists, wondering whether the wild-and-crazy little vessel—or one like her—will indeed be marketable at some point in the future. "We'll just have to wait and see," concluded Weyant.

For more information on Sea Ray, including contact information, click here.

This article originally appeared in the January 2009 issue of Power & Motoryacht magazine.

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