Showcasing Suzuki’s advanced technologies and designs, Suzuki’s flagship DF300 outboard has been recognized twice as the most innovative outboard in the industry. The original DF300 was launched as the world’s first 220.7kW (300PS) 4-stroke outboard and was acknowledged for this by the National Marine Manufacturers Association (NMMA) with its 2006 Innovation Award.
The new DF300AP incorporates several new features, the most notable being Suzuki Selective Rotation. By strengthening the lower unit’s forward and reverse gearing, Suzuki engineers have designed a lower unit for the DF300AP that will run in either right or left rotation. With this world’s first feature, the DF300AP was recognized once again with the 2012 NMMA Innovation Award.
The DF250AP is based on the DF300AP and shares the same award winning innovations and designs of Suzuki’s flagship outboard. Advanced features like Suzuki Selective Rotation, Suzuki Precision Control, and Suzuki Lean Burn Control, plus big V6 power combine to provide boaters with outstanding performance and great convenience.
New Lower Unit
Compared to the original DF300, the biggest changes you’ll find on these outboards are in the lower unit, which was redesigned for the Suzuki Selective Rotation system—the world’s first integration of regular and counter-rotation models into a single unit. The system consists of a new drive gear layout in the lower unit that allows the outboard to operate in either regular or counter-rotation mode, and a switch that connects to a circuit in the engine compartment that engages the counter-rotation mode. Like the DF300, the new DF300AP/250AP utilizes an aggressive final drive ratio of 2.08:1 allowing it to turn a 406mm (16-inch) diameter propeller available in various pitch size for optimum performance on a wide variety of boats. Changes to gear designs provide greater durability, and adding a two-way water inlet changes water flow into the cooling system for increased cooling efficiency.
Suzuki Selective Rotation
In multi-outboard installations on large boats, a counter-rotation outboard is usually paired with a regular rotation model to help keep the boat traveling on an even keel and in a straight line. The DF300AP/250AP is built with special counter-rotating gearing in the lower unit, which causes the prop to rotate in the opposite direction. Suzuki Selective Rotation eliminates the need to purchase a dedicated counter-rotation outboard by using a special switch that when connected to a circuit inside of the engine compartment, turns a regular rotation outboard into a counter-rotation model with a counter rotational propeller.* This industry first is made possible through a special, unified design of gears, shaft, and bearings in the lower unit that are designed to operate reliably and efficiently in either regular or counter-rotation directions.
With the addition of Suzuki Selective Rotation, gears in the lower unit were redesigned using a different alloy and slightly larger diameters delivering greater rigidity. The gears are specially heat treated creating gears that are highly durable.
Two-way Water Inlet
The engine’s cooling system relies on water supplied through low water intakes located on the lower unit. Utilizing this dual low water inlet configuration increases water flow into the lower unit, which delivers greater cooling efficiency. Positioning the forward inlet at the gear case nose delivers a greater water supply especially at high speeds. The second inlet is also positioned lower allowing the DF300AP/250AP to operate in shallow water conditions.
Newly Designed Low Drag Gear Case
The new DF300AP/250AP features a redesigned low drag gear case developed to accommodate the new gears utilized in the Suzuki Selective Rotation system. The case itself is actually larger than the previous model to provide increased gear durability, however it is designed with a smoother, more hydrodynamic shape that allows it to move through the water with less drag and greater efficiency. Areas with the highest drag are indicated in red in the illustrations below. The comparison shows that the new design allows the lower unit to slice through the water with less drag.
Suzuki’s Advanced Technology Delivers the Utmost in Performance VVT (Variable Valve Timing)
Suzuki’s engineers designed the 4.0-liter V6 engine with an aggressive cam profile that delivers maximum output and performance at high rpm. In coupling this cam profile with Suzuki’s advanced Variable Valve Timing (VVT), the DF300AP/250AP delivers the additional torque that outboards need for accelerating in the low to mid-range. VVT achieves this by adjusting the timing of the intake valves, allowing them to open before the exhaust valves are fully closed, creating a momentary overlap in the timing where both sets of valves are open. Using VVT, this overlap can be increased or decreased by altering intake timing with the camshaft resulting in optimum timing for low and mid-range operation.
32-Bit ECM and Suzuki’s Multi Point Sequential Electronic Fuel Injection
Suzuki pioneered the use of multi-point sequential electronic fuel injection in four-stroke outboards with the introduction of the original DF60 and DF70. At the heart of the DF300AP/250AP’s multi point sequential fuel injection system is the ECM (Engine Control Module), which constantly monitors a large amount of data, in real time, from a series of sensors placed in critical areas on the engine. This comprehensive network of sensors includes the Manifold Absolute Pressure Sensor, Crankshaft Position Sensor, Intake Air Temperature Sensor, Cylinder Wall Temperature Sensor, Camshaft Position Sensor, and Exhaust Jacket Temperature Sensor. Using a very powerful 32-bit computer, the ECM processes data from all of these sensors and instantly calculates the optimum amount of fuel to be injected at high pressure into each of the V6’s cylinders by the multi point sequential fuel injection system. Benefits of this system include reduced exhaust emissions, which allow the DF300AP/250AP to comply with the California Air Resource Board (CARB) 3-Star emission requirements, lower fuel consumption, smoother starts, crisper acceleration, smoother performance, and maximum efficiency.
Suzuki Precision Control (Electronic Throttle and Shift Systems)
Suzuki Precision Control is a technologically advanced computer-based control system that replaces the mechanical control cables found in conventional control systems with electronic wiring that eliminates the source of friction and resistance. While you enjoy smooth, little friction throttle and shift operation, the system’s computer is processing and transmitting commands in real-time to actuators at the engine that deliver precise throttle controls with smoother, decisive shifting. This is most evident in the low rpm range where operation is noticeably smooth and accurate. When combined with Suzuki’s Lean Burn Control System it allows control of fuel and air flow to boost the limit of the controllable revolution range improving fuel economy over a wide operating range. Suzuki Precision Control also features built-in systems that help guard the engine and drive against damage due to mishandling, and its design and simple wiring make installation easy, reducing the time required for rigging and adjustment. The system offers precision control for single, twin or triple installation as well as dual station operation.
Long Track Intake Manifold
Another performance enhancing feature on the DF300AP/250AP is a tuned long track intake manifold. Using long intake pipes tuned to provide smooth airflow into the engine the system provides the DF300AP/250AP with enhanced low-end power.
Large Air Intake with Water Separator
The DF300AP/250AP is designed with a large air induction port to maximize airflow into the engine in order to obtain maximum power output. The increased airflow produces more low- to mid-range torque and provides a wide power band that is necessary in an outboard engine. Suzuki also designed the system with a water separator, which aids in keeping water out of the electronic throttle body and a heat shield to keep intake air from being heated by the engine.
Spherical Bore Throttle Body
An 81mm spherical bore throttle body smoothes the turbulent airflow into the engine that occurs as the throttle begins to open. Providing a smoother airflow during acceleration results in increased throttle control and stable engine operation at low rpm.
The cooler the fuel the denser it is, and the denser it is the better performance it delivers. Incorporating a fuel cooler in the DF300AP/250AP’s fuel delivery system cools the fuel before it enters the engine. Providing the engine with an optimum fuel supply results in better combustion and more performance.
Strengthened Forged Pistons
The upper portion of pistons used in the big V6 engine is treated with an alumite coating that increases heat resistance. A resin coating applied to the piston skirt increases resistance to wear and reduces friction.
Suzuki outboards are among the compact outboards in their respective classes. That’s due in part to the utilization of Suzuki’s proven offset driveshaft system. This design places the crankshaft in front of the driveshaft through the use of intermediate gear reduction. In addition to providing an increase in power performance and adding to the compactness of the outboard, this system moves the outboard’s center of gravity forward, resulting in contribution to weight distribution, balance, directional stability, and less vibration.
Two-Stage Cam Drive System
The DF300AP/250AP utilizes a two-stage cam drive system that incorporates both gears and a chain. First stage gears transfer power between the crankshaft and the drive shaft from which a second stage utilizes a chain to deliver power from the driveshaft to the camshaft. This system allows for the use of smaller cam sprockets, which in turn allow for a reduction in valve angles also reducing the size of the cylinder head. An automatic hydraulic tensioner incorporated into the timing chain system keeps the chain properly tensioned and provides years of maintenance-free operation.
Suzuki Water Detecting System
Water in the fuel can be the source of poor combustion, lower power output, and corrosion. To help protect the engine from moisture in the fuel, the DF300AP/250AP is the first Suzuki outboard to utilize a water detecting fuel filter that alerts the operator with both visual and audio warnings when water is present in the fuel.
Water-Cooled Voltage Regulator
The outboard’s electric system includes a water-cooled voltage regulator that dissipates heat in the regulator to enhance engine durability.
Fuses protecting the DF300AP/250AP’s electric system are assembled into a single fuse box located under the cowling on the side front-port of the outboard motor, which provides convenient access while offering a clean exterior.
Highly Reliable Direct Ignition System
Supplying spark to the big V6 engine is an advanced ignition system that utilizes integral type spark plug caps with built-in ignition coils. The system is controlled by the outboard’s powerful 32-bit computer and provides each cylinder with optimum spark timing. In addition to reducing the number of parts and simplifying the wiring system, this arrangement greatly reduces electronic engine “noise” that can interfere with VHF radios, fish finders, and other marine electronics.
Easier Maintenance Dual Engine Flush Ports
The buildup of sand and salt in the engine’s cooling system can lead to engine damage. To aid in reducing such buildup, the DF300AP/250AP is designed with two freshwater flush ports that make flushing of the cooling system as convenient and easy as possible. With one port located on the rear panel and the second on the front panel, access is easy and flushing out the system is possible whether the boat is in or out of the water.
Convenient Dual Circuit Charging System
The DF300AP/250AP incorporates a dual circuit charging system that can be adapted* to accommodate the dual-battery configurations often used on large boats. When used in this configuration the system is designed to charge both the main and auxiliary batteries simultaneously but on independent circuits. With this you can drain down the accessory battery powering your electronics and still have a fully charged main battery for starting the motor.
Suzuki Troll Mode System (Optional Equipment)
Suzuki’s Troll Mode system provides finer control over engine speed at low rpms to keep your boat moving at a constant speed while trolling. When the system is engaged, revs are controlled with an independent control switch that adjusts engine revs in 50rpm increments over a range spanning from idle to 1,200 rpm. The system includes a control switch, which can be mounted nearly anywhere on the console, and a tachometer, and is compatible with Suzuki’s SMIS digital gauges or the dual scale analog gauges.