This article originally appeared in an internal report for ZF Marine Propulsion Systems. It is being republished here with permission. All lead image collage photos by Seven Marine. All other images by IDM Photography LLC.
557 horsepower. V8 Engines with this much power were once only reserved for high end sports cars such as the Cadillac CTS –V and the likes of off shore racers on the ocean. As technology advances parts become lighter and stronger, and engines steadily become more fuel efficient while producing more power and more torque all in smaller packages. Its because of the lightness of the new generation of V8 engines, that today 557 horsepower (410 kw) can now be found hidden beneath the cowl of a very special marine outboard motor, the Seven Marine 557.
Seven Marine was born out of a combination of decades engineering outboard motors and a passion for speed bred in automotive racing. Rick Davis, Seven Marine’s President, spent more than 20 years as VP of Engine Design and as the Chief Technical Officer at Mercury Marine before retiring in 2008. Rick is also an avid vintage racecar driver. Rounding out the original Seven Marine team are Rick’s two sons Brian and Eric. Both boys share their father’s love of speed, starting early in the seat of racing go-karts.
None of what Seven Marine has accomplished would be possible without the nagging idea that son Eric had to make a high-performance outboard unlike anything in the market. Eric’s concept was to mate a powerful V8 with a transmission that could handle the power, all packaged in a transom mounted outboard motor. After a few months incessantly pestering both Rick and Brian, who both tried to pass off the idea as crazy, Eric finally put together a few CAD drawings of an LS9 Corvette engine and a transmission in an outboard motor configuration. Incredibly, the mechanics of the entire unit (weight, connectivity, support, and power output) aligned in the schematic within a few inches of each other. This was the “it” moment for Rick, “ I looked at Eric’s drawings and realized everything lined up almost perfectly. That was something I could work with.”
To make this motor a reality, Rick needed to find partners that were willing to work with him. “There was no way we were going to get this concept off the ground without partners who were willing to work with us.” Through Rick’s long time relationship with ZF Marine, he knew this would be the partner he needed to harness the engine’s power. A call to the management team at ZF and a presentation of the concept was enough to convince the ZF Marine team to get on board. The next call was to General Motors, this would be a much tougher challenge. Luckily, the gentleman responsible for the engine family that Rick wanted for his outboard was a boater at heart. “It probably saved us from getting our proposal tossed in the garbage.” Laughs Rick, but GM wanted more. Shortly after Rick and sons presented GM with a solid design concept, and, along with the commitment from ZF Marine to support the project, sealed the deal for GM to partner with Seven Marine.
The soul of the 557 is a delicate balance of marine outboard motor niche marketing ingenuity, world-class engineering, and the unfailing belief that they could shoehorn an all aluminum 6.2L supercharged small-block V8 inside the cowl. One of the big challenges was to design a cradle that allowed the V8 to sit in a natural horizontal position on the top of the motor while aligning the transmission, and the rest of the driveline directly below the V8. The feat of engineering that allows for the configuration to work while also adding the benefit of structural stability is the transfer case. The 557’s transfer case is designed to allow for quick and easy ratio changes while helical gears, also supplied by ZF, transfer power quietly and efficiently from the engine to the transmission.
After the V8 was in place with the transfer case, a custom 3.5” dual exhaust was designed to cascade out of the V8 and down along the body of the motor. Seven Marine has tuned the exhaust to be powerful and crisp while not displeasing at cruising speeds. It’s a beautiful display of engine noise usually reserved for aftermarket automotive tuners. Chrome exhaust tips pander to the motor’s tuner car aesthetic nicely.
The power of the GM engine meant that traditional outboard shifting technology would not work. Rick was familiar with the ZF POD 2800 and its unique right angle transmission and he had a hunch it would work perfectly in the 557. The transmission that Rick wanted to use was designed for inboard applications so it needed to be modified to fit the outboard 557 design. ZF Marine’s application engineers worked closely with Rick and his team to accommodate their unique needs, and transformed one of their newest inboard transmissions into their newest outboard transmission. The electronically controlled, hydraulically shifted transmission has resulted in seamless shift technology for the outboard. According to Rick, this is a revelation in outboard technology. “There’s no “clunk” like you get in a traditional outboard transmission. You just move the gear lever forward, there’s a swish of water, and the boat moves forward. Inboard boat owners aren’t surprised by this, but outboard boat owners are stunned by it.” The other benefit of the integration of the ZF transmission, was the ability to offer proven ZF Marine electronic controls as well as the Joystick Maneuvering System.
With a price tag hovering right around $70K, the motor is aimed at the boater who is looking to spend money to create a faster experience on the water. “For these guys (Seven Marine’s customers), life on the water begins at 60mph”, explained Rick. Many new customers are opting for twin 557’s instead of three and sometimes four 300-350 hp (220-257kw) outboard engines. The power output of the 557, the reduction in weight from multiple engines to two, and less overall drag in the water, is allowing customers to go much faster while having the added bonus of saving on fuel.
Seven Marine customers are typically into competitive offshore fishing. The 557s are capable of getting boats to the fishing grounds first and back to the marina sooner. Seven Marine customers might own a Sportfishing Yacht and are looking for a powerful Center Console boat as a second complimentary fishing platform.
The motor seems to have found a hungry audience in customers who have become weary of the competitors motor’s significantly lower output. When the difference in cruising speed is 40 mph with triple 350’s versus 60 mph with twin 557’s, the decision seems easy.
The most intriguing aspect to the Seven Marine motors, beside their unbridled power output, is the ability to customize the cowl of each motor to fit a client’s needs. Each cowl is painted right at the factory and Seven Marine has the ability to match boat graphics or a customer’s favorite colors. Taking a page out of the automotive custom market meant that Seven Marine could be an even more sought after niche product. Rick pointed out that “the ability to create cool styling and custom paint was our way to further the boat builder's desire to delight his customer”.
From it’s very inception, Seven Motors has designed the entire 557 package to be groundbreaking. From simple considerations, such as designing the cowl for easy access to all fluid filters for ease of maintenance, to complex design challenges , such as building a robust mounting system that can not only handle the weight and trim tasks of the 1,100lb (500kg) motor sitting on the transom, but also incorporate its hydraulic steering. Seven Marine has set out not to simply best the outboard motor segment but to re-establish the benchmark.
“We saw the growing market of large center console boats and their increasing lengths. More power wasn’t only desired, it was required. This created a new white space for the "Cadillac" of outboards, We’ve delivered a special product specific to the needs of this segment, enabled by supercharged GM power and an integrated ZF transmission and control system.”
Pretty impressive accomplishments for a company that literally started out with a father and two sons sitting at the 2010 Miami International Boat Show sporting embroidered golf shirts, new business cards, and a brochure with the ink barely dry. It took only three years from CAD layouts to delivery of the first engine. An astounding accomplishment in any market.
Videos of the engines in action are below: