The new DF350A from Suzuki represents the third brand of 350 hp outboard to hit the market, joining Mercury’s 350 Verado and Yamaha F350. With this motor, Suzuki is aiming a large portion of its attention toward big center consoles with triple and quadruple outboards. The motor will also find application on the growing number of large bay boats.
This 350 V-6 offers a number of innovative features, the most obvious is a pair of contra-rotating three-blade propellers. This helps boost holeshot, minimizes prop torque, grips better in tight turns, and improves low-speed handling in forward or reverse. Contra-rotating props also negate the need to mix right- and left-hand rotating motors in multi-outboard installations.
The contra-rotating props also help distribute torque across two inline gears that are smaller in diameter than would be necessary with a single prop. This helps keep the gear case as small and hydrodynamic as possible to reduce drag, increase efficiency and boost top speed. Suzuki engineers also repositioned the primary cooling water pickup to the front of the bullet, with secondary pickup on the underside, just forward of the skeg.
To increase the power output of the 4.4-liter block (up 0.4 liters from the existing Suzuki 300), the engineering team increased the compression ratio to 12:1 — the highest so far for an outboard. To prevent knock with such compression, the DF350A features an intake in the hood that feeds air directly to the engine. This keeps the air as cool as possible (a key to preventing knock), while a series of small louvers whisk away moisture before the air is fed to the engine.
Two fuel injectors per cylinder simultaneously deliver a finely atomized charge of fuel. This promotes more efficient combustion, and also cools the intake air more effectively than a single injector, further preventing knock.
The new 350 carries over a number of features from the 300, including electronic throttle and shift for smoother control, Lean Burn to maximize fuel efficiency, an offset drive shaft that shifts the center of gravity forward, two-gear reduction to help keep the gear case compact, variable valve timing for optimal low- and mid-speed power and efficiency, and a self-adjusting timing chain that requires no maintenance.
I ran a Freeman 37 with quad DF350As in the Atlantic waters outside Boca Raton, Florida, last week. With 30-inch-pitch stainless-steel prop sets, the Freeman vaulted from zero to 30 mph in 8.3 seconds and reached a top speed of 70 mph at 6,200 rpm. The most economical cruising speed occurred at 3,400 rpm and 35 mpg where the four engines burned 31.8 gallons per hour for 1.1 mpg.
The Suzuki 350 is available in XL (25-inch-shaft) and XXL (30-inch-shaft) models, which weigh 727 and 747 pounds, respectively. You can get the DF350A in two colors: pearl nebular black and cool white. Pricing was unavailable at press time.