New Suzuki DF350A with duo prop is the brand's biggest outboard yet

Suzuki Motor Corporation has unveiled its new DF350A flagship outboard. With realised horsepower of 350hp, it’s the maximum output in Suzuki’s four-stroke line-up of outboards and there's a lot of great technology behind the flagship.

For the first time for Suzuki outboards, the DF350A adopts a dual contra-rotating propeller system. In the so-called Suzuki Dual Prop System, twin propellers on the one outboard more efficiently transmit forward thrust to enhance acceleration and directional stability.

Suzuki says its new three-blade front/three-blade back propeller provided not only the highest recorded speeds for the DF350A, but also delivered incredible acceleration, even under heavy load and at high rotation speeds.

By optimising the shape of the gearcase and using a contra-rotating or duo prop, the DF350A boasts powerful acceleration that you wouldn’t ordinarily expect from a modest displacement engine, the Japanese engine maker adds.

Given that it’s not unlike the Duoprop system used by sterndrive manufacturers, we’d also expect less torque at the wheel going forward and improved manoeuvrability in reverse in single-screw and multi-outboard set-ups, too.

PROVEN FOUNDATIONS
Based on the proven engineering of the DF300AP and its V6 55 degree block, the new DF350A has 4.4L displacement (an increase from 4.0L), as the stroke is up from 89mm to 97mm. An upshot is that the engine remains compact in multiple installations and as a repower for 300hp units.

"The concept is a 350 horsepower engine that DF300AP users can rig easily on their boat. Then, V6 with a narrow 55-degree bank angle becomes our unavoidable condition. We planned to keep the bore pitch 108mm to be the same as our reliable and durable DF300AP. This was the starting point of development," explains Katsuhiro Fukuda, Chief Engineer at Suzuki.

The new DF350A achieves 80hp per displacement litre (up from 75hp per litre on the 300) via improved combustion and, for the first time on an outboard engine, a compression ratio of 12.0:1.

"Our solution to developing 80 horsepower per litre in a V6 350 horsepower engine was to increase the compression ratio to 12.0:1, the highest compression ratio ever for a production outboard engine," says Fukuda.

In order to make this work without knocking (a typical problem at this ratio), Suzuki developed a Dual Injector System to mix cooler air with well-atomised fuel to provide optimal conditions for complete and controlled combustion. The result is an increase in power of 3 per cent.

"Although using the same 55-degree bank, DF350A reflects 10 years of evolution in every detail. Even a single head bolt is newly designed," Fukuda adds.

AIR AND WATER INTAKES
In addition to a high compression ratio, the newly-developed four-stroke V6-cylinder engine is equipped with features such as the Direct Intake System to realise high-output performance and improved fuel efficiency.

The DF350A is equipped with a double louvre at the air intake to remove water from the air taken into cowl. This also gives the DF350A its contemporary ‘hooded’ look.

Meanwhile, the engine’s cooling system relies on water supplied through low water intakes located on the lower unit as per usual, but there is a dual low water inlet configuration to increase water flow and improve cooling efficiency.

Positioning the forward inlet by the gearcase nose delivers a greater water supply, especially at high speeds, Suzuki says. The second inlet is also positioned lower, allowing the DF350A to operate in shallow water in, say, flats fishing situations common around Florida.

BIG HP, BIG FEATURES
The main features of the newly-developed maximum 350hp Suzuki DF350A outboard engine include:
>> Compact, 4390cm3 four-stroke V6-cylinder engine
>>High compression ratio of 12.0 is adopted for the first time on Suzuki outboards, improving combustion efficiency to realise horsepower of 350PS, the maximum output in Suzuki’s line-up of outboards
>> Suzuki’s unique Direct Intake System, which efficiently takes in outside air into the engine, and Suzuki Dual Louver System are adopted
>> Dual injectors per cylinder and optimal combustion chamber shape increase charging efficiency and combustion efficiency to realise superb output performance
>> Contra-rotating propellers that create the Suzuki Dual Prop System. A smaller gear case decreases underwater resistance to realise high running performance and directional stability.
>> To top it off, the DF350A has sporty, aggressive, and innovative styling perfect for a flagship model and which ushers in Suzuki’s next-generation outboards.

THE GLOBAL UNVEILING AND RELEASE
At the unveiling event held in Miami, (June 9, 2017), the President of Suzuki Motor Corporation, Toshihiro Suzuki,  acknowledged that outboards play important role in Suzuki’s business.

"The DF350A is a model that clearly illustrates our brand slogan — ‘The Ultimate 4-Stroke Outboard,’" he said.

DF350A will be produced at the Toyokawa Plant in Japan and will be launched in the USA from July 2017. The global roll-out will following soon after.

More in this promo video...

Specifications: Suzuki DF350A
Engine Type: DOHC 24-valve
Number of Cylinders: V6 55 degree
Piston Displacement: 4390cc
Bore x Stroke: 98mm x 97mm
Gear Ratio: 2.29:1
Gear Shift: F-N-R Drive by Wire
Fuel Delivery System: Multipoint sequential electronic fuel injection
Maximum Output: 257kW@6000pm
Full Throttle WOT range: 5700-6300rpm
Shaft Length: X 25in, XX 30in
Starting System: Electric
Weight: 330kg
Oil Pan: 8.0lt
Ignition: Fully transistorised
Alternator: 12C 54A
Engine Mounting: Shear Mount
Trim Method: Power Trim and Tilt
Exhaust: Though-Prop
Propellers: TBA
Warranty: Five Years Recreational
More at this global Suzuki page.