Seven Marine 557 Outboard Update
New transfer case will enable drive-ratio changes
ANOTHER UPDATE: The 557 is in the water and on the market as of February 2012. For a full report, see Seven Marine 557 Outboard: In-Water Debut.
Seven Marine is making some design updates to its 557-hp, Cadillac V8-powered outboard before it begins sea trials, according to Seven Marine vice president Brian Davis, who spoke to me on April 13. We reported in February on the Miami Boat Show debut (“Seven Marine Reveals 557HP Outboard at Miami Show”) of this new technology. Since then, the Seven Marine team has been busy back in its Mequon, Wis., shop.
“We are responding to feedback and inquires we’ve received since the Miami show,” said Davis. “We found that people with a wide variety of hull types are interested in the Seven 557, so we are making some updates to allow the motor’s final drive ratio to be more flexible.”
On most current outboard motors, adjustment of the final drive ratio can be accomplished by changing the gear ratio in the lower unit, and changing the propeller. The Seven 557 offers a third opportunity, because it has a transfer case between its horizontal V8 and the transmission, which is located below the engine. Davis told me that after meeting with suppliers, Seven is modifying the transfer case to permit relatively quick and easy adjustment of the ratio between the engine and transmission.
“This will allow the Seven 557 to be set up for a wide-and-heavy boat that might have traditionally had inboard power, or for a fast, narrow hull where speed is the ultimate goal,” said Davis. “We’ve had interest from both markets.”
Once the update to the transfer case is accomplished, Seven will complete an industry-standard regimen of testing that will combine bench testing of components, static tank testing, and sea trials. Davis says that during sea trials, he hopes to document what he expects will be exceptional fuel economy from the Seven 557 motors at cruising speeds.
“I think that at 40 mph, these motors will be more fuel efficient than other 1,000-hp engine options,” said Davis, “whether that’s inboards or multiple outboards. The Cadillac engines are very efficient at that rpm.”
Seven Marine is also pushing the notion that a pair of its big outboards could replace pod-drive inboards on large fishing boats. The outboards may be lighter in weight, less expensive, and be located on the transom rather than within the boat, creating more space for an aft cabin or a lower cockpit deck. This is the same pitch Yamaha has successfully made for its 350-hp, 5.7-liter V8 F350, but Seven Marine will be able to offer more power and joystick docking control.
But first, Seven needs to get its mega-motors in the water and prove they really work. Stay tuned.
- Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. He is a former editor at Boating Magazine and contributor to many national publications since 1986.
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