Skip to main content

2011 Engines Review - Outboard


The Alpha Outboard

A group of Midwestern engineers think they’ve built the great white shark of motors.


The 557 puts out about 60 percent more power than the next nearest outboard.

Is this evolution or revolution? That’s what I thought to myself when the press release in my e-mail inbox announced that the most powerful outboard engine ever built was going to debut at the Miami International Boat Show. It was a boastful claim and one that piqued both my professional and personal curiosity, as all of my boats have been outboard-powered.

At the show I stared at the two massive motors and their streamlined, polished-to-perfection, hinged engine cowlings, hanging on the transom of a 37-foot Intrepid. Offering a combined 1,114 hp, these powerplants, which represent a quantum leap in big-outboard technology, come from a company called Seven Marine. Each engine is rated at 557 hp, more than 200-hp more than the next closest outboard. Why would someone build a motor whose capabilities are so far beyond anything currently available?

Anyone who follows the center console and/or walkaround boat market has surely noticed that these vessels have been getting bigger and bigger, and that to maintain performance, multiple-outboard engine installations have become de rigueur. And I don’t mean just twins. I’ve seen plenty of 40-foot-plus speedsters with three, four, and even five 300-hp and 350-hp outboards strapped to the back. And the aforementioned Intrepid has a 54-footer on its drawing board that’ll be offered with outboard power.


Photos Courtesy of Seven Marine

Left to right: Sandy Ballou, Rick Davis, and Eric Davis are the men behind Seven Marine’s V-8 outboard.

There’s a market for large outboards also because these engines are relatively light and easy to service and replace if something goes wrong. But truth be told, vessels with multiple outboards don’t ever see the true horsepower produced by those motors. An outboard’s lower gear case is a source of drag, which means that a single outboard is actually the most efficient setup. Each time you bolt on another motor you add horsepower but you also add underwater drag. So the actual percentage of gain in horsepower decreases with each additional powerplant.

That’s why Seven Marine’s vice president Brian Davis says two high-horsepower outboards are the optimum setup. They produce less drag and so are more efficient, while still providing added safety offshore in the form of redundancy. Two of them weigh less than triple and quad installations yet have comparable or even more total horsepower. The 557—its model name is also its horsepower rating—is only about 100 pounds heavier than a 300- to 350-hp four-stroke outboard. Davis says the company’s goal is to get 60 percent more power than the current largest outboard available and come within ten percent of its weight. It sure looks like they suceeded.


Note the 557’s easy access hinged cowling.

Like all outboards, each $68,900 (list) 557 is virtually all aluminum, but unlike them, it’s not directly cooled by seawater. Instead it has a closed-loop cooling system, which Seven Marine says is the first of its kind in an outboard, and ethylene glycol, the same coolant used in your car. The system works by pulling salt water into dual water inlets at the bottom of the lower unit via a seawater pump. The water circulates through a heat exchanger where the ethylene glycol is flowing in a separate loop. Heat passes from the glycol to the seawater through the metal casing, keeping the motor’s temperature in check. (It works like the cool air flowing over a car radiator.) The water exits the motor and returns to the sea without ever touching the engine.

Speaking of cars, it was actually an automobile that allowed this marine project to become a reality. The 557 began life under the hood of a Cadillac CTS-V—it’s a marinized version of that car’s supercharged 6.2-liter V-8, mounted horizontally, just as it is in the automotive setting, and transmitting its power down to a ZF transmission via a transfer case assembly. Unlike most outboards, where shifting is done in the lower gear case, this motor’s gear changes occur in the midsection, which then routes power down to a lower gear case that has twin pinion gears to ensure durability.


Each spark plug connects directly to an ignition coil.

Another revolutionary feature of the 557 is its ZF fly-by-wire JMS (Joystick Maneuvering System). Using it, the two motors and bow thruster work in concert to slide a boat sideways, spin it on her axis, and basically put her just about anywhere you want. Davis says with the popularity of pod drives, the company wanted to offer the advantages of a pod-type system with its motors.

Although Seven Marine seems to have appeared out of left field, the company is actually comprised of veteran marine-engine specialists like Rick Davis (Brian’s dad), who is the former chief technology officer for Mercury Marine and was involved in the development of the four-stroke Verado outboard and Zeus pod drive. Manufacturing expert Sandy Ballou and the man
behind the 557’s concept, Eric Davis (Rick’s son),
make up the rest of this team of engineering wizards.


The first joystick-equipped outboard is said to offer pod-like maneuverability.

Every once in a while you see something that opens your eyes to what’s possible. That thing often comes from the minds of people who don’t simply see limits—they work from the premise, “Wouldn’t it be great if…” and then make it happen. Seven Marine and its 557-hp motor are the result of that kind of thinking. It’s a project that shows how the path not taken can be damn exciting. And from the looks of it, damn fast too.

Seven Marine
(877) 777-0330.

This article originally appeared in the June 2011 issue of Power & Motoryacht magazine.