Rated at 557 ponies, 59 percent more power than its closest rival, Seven Marine’s 557 is the world’s most powerful outboard. This brute is based on a supercharged, 6.2-liter, aluminum Cadillac LSA V-8. It’s the only outboard with a closed cooling system, a key anti-corrosion feature.
The horizontal powerhead turns the drivetrain 90 degrees through a ZF Marine electronic transmission, a derivative of the gearbox used in ZF’s pod drives. The 557 can be had with gear ratios ranging from 1.4:1 to 2.1:1.
The beefy, twin-pinion lower unit accommodates propellers up to 18 inches in diameter, ensuring delivery of the engine’s 550 foot-pounds of torque. The 557 also features dual exhaust outlets; at low speeds, exhaust gases exit through ports above water. As speed increases, this transitions to a through-hub exhaust. There are also dual water inlets. The 557’s 150-amp alternator surpasses the output of any other outboard. Integral power-assist steering, co-developed with Latham Marine, helps rein in the torque. The 1,045-pound 557 weighs 282 pounds more than Yamaha’s 763-pound F350 V-8. The 557’s power-to-weight ratio is 0.53 — 15 percent more than that of Yamaha’s and equivalent to Mercury Racing’s Verado 350 SCi. It’s 7 percent lower than that of Evinrude’s E-TEC 300.