Suzuki DF250APX Specifications
| Engine Model: Suzuki DF250APX |
| Engine Type: 4-stroke 6-cylinder DOHC 24-valve gasoline outboard engine |
| Total Displacement: 250 cu.in (4 L) |
| Rated Engine Power: 250 Hp (184 kW) at 6000 rpm |
| Fuel System: Multi point sequential electronic fuel injection |
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The Suzuki DF250APX is a technologically
advanced outboard that delivers premium power and precise control in a
package optimized for 25-inch transoms. Based on the flagship DF300AP
platform, it incorporates Suzuki's Selective Rotation, which through a
special switch and circuit inside the engine compartment transforms a
regular rotation outboard into a counter-rotation model when paired with
a counter-rotational propeller.
The engine features a 55-degree V6 block with Dual Overhead Cams (DOHC)
and 24 valves, ensuring robust power delivery. Suzuki's Lean Burn
Control System works in concert with the electronic Precision Control
throttle and shift to optimize fuel efficiency across a wide operating
range, from low-speed trolling to cruising speeds, with in-house testing
showing the DF300AP is 14 percent more economical than the original
non-Lean Burn DF300 without sacrificing power.
A redesigned low-drag lower unit with an aggressive 2.08:1 gear ratio,
dual water inlets for enhanced cooling, and a suite of advanced features
like Variable Valve Timing (VVT) and a water-detecting fuel system make
the DF250APX a durable, efficient, and high-performing choice for
serious boaters.
Engine Model: Suzuki DF250APX
Engine Type: 4-Stroke, 55° V6, DOHC (Double Overhead Camshaft), 24-Valve
Number of Cylinders: 6
Valve Train Drive: Self-adjusting oil-bathed timing chain with automatic
hydraulic tensioner
Bore and Stroke: 98.0 mm x 89.0 mm (3.86 in x 3.50 in)
Piston Displacement: 4028 cc (250 cu. in)
Maximum Output: 184 kW (250 Hp)
Full Throttle Operating Range: 5500-6100 rpm
Fuel Delivery System: Multi-Point Sequential Electronic Fuel Injection
with Lean Burn and Oxygen Sensor Feedback
Alternator: 12V 54A
Trim Method: Power Trim and Tilt
Gear Ratio: 2.08:1 (Two-stage Reduction Gear)
Gear Shift: F-N-R (Forward-Neutral-Reverse) via Suzuki Precision Control
Control System: Suzuki Precision Control (Drive-by-Wire)
Exhaust: Through Prop Hub Exhaust
Propeller Selection: 15"-27.5" (Standard Rotation); 17"-26" (Counter
Rotation)
Starting System: Electric with Suzuki Start System
Ignition System: Fully-transistorized Solid State Direct Ignition
Engine Lubrication: Trochoid pump pressure lubrication
Engine Oil Capacity: 8.0 L (8.5 US qt.)
Gearcase Oil Capacity: 1.1 L (1.2 US qt.)
Fuel Type: Automotive unleaded gasoline (89-94 research octane
recommended)
Spark Plugs: NGK BKR6E
CARB Emissions Rating: 3-Star Ultra-Low
The DF250APX is built around a potent 4.0-liter V6 powerhead with a
narrow 55-degree bank angle, contributing to its remarkably compact
dimensions. The block is engineered for high performance and durability,
utilizing strengthened components throughout. The powerhead incorporates
a DOHC 24-valve configuration for optimal airflow and combustion
efficiency.
A key innovation is the two-stage cam drive system, which first uses
gears to transfer power from the crankshaft to a driveshaft, and then a
self-adjusting, oil-bathed timing chain with an automatic hydraulic
tensioner to drive the camshafts. This design allows for a more compact
cylinder head and provides maintenance-free operation for the life of
the engine.
Suzuki's Variable Valve Timing (VVT) system, hydraulically controlled by
oil pressure, optimizes intake valve timing to maximize torque in the
low and mid-range. The system automatically adjusts valve timing by
altering intake camshaft timing, creating momentary overlap where both
intake and exhaust valves are open, resulting in optimum timing for low
and mid-range operation. This delivers the robust acceleration essential
for outboard applications.
The offset driveshaft design, pioneered by Suzuki, positions the
crankshaft in front of the driveshaft, simultaneously moving the
outboard's center of gravity forward. While this design contributes
greatly to the outboard's overall compactness and increased power
performance, it also moves the engine's axis of inertia, the point where
engine vibrations are at a minimum, up over the upper engine mount,
greatly reducing vibration.
The DF250APX's fuel system is highly advanced, centered on the Suzuki
Lean Burn Control System. This technology uses an O2 sensor feedback
loop to predict fuel needs according to operating conditions, allowing
the engine to run on a more efficient, leaner air-fuel mixture from
low-speed operation through the cruising range. This system delivers its
benefits over a wide operating range, providing significant improvements
in fuel economy from low-speed operation into the cruising range.
This system works seamlessly with the Multi-Point Sequential Electronic
Fuel Injection, which precisely meters fuel to each cylinder for optimal
combustion. The O2 Sensor Feedback Control System enables cleaner and
more stable emissions by controlling the air-fuel ratio across each of
the engine's operating ranges.
Additional fuel system enhancements include a fuel cooler that cools
fuel before it enters the engine, increasing fuel density for better
combustion and improved performance. An 81mm spherical bore throttle
body smoothes the turbulent airflow into the engine that occurs as the
throttle begins to open, providing increased throttle control and stable
engine operation at low rpm. The engine also features a large air intake
with a water separator to keep moisture out of the electronic throttle
body and a heat shield to prevent intake air from being heated by the
engine.
The DF250APX employs a trochoid pump pressure lubrication system to
ensure consistent and reliable pressurized oil delivery to all critical
engine components, including the crankshaft, connecting rods, and the
valve train with its VVT components. The engine has a substantial oil
capacity of 8.0 liters.
Cooling efficiency is enhanced by a dual water inlet system, a
significant feature of the DF250APX. By positioning one water intake at
the gearcase nose and a second lower intake, the system increases water
flow into the lower unit, delivering greater cooling efficiency.
The forward inlet at the gear case nose delivers a greater water supply
especially at high speeds, while the second inlet is also positioned
lower allowing the engine to operate in shallow water conditions.
For post-operation maintenance, the DF250APX is equipped with freshwater
flushing ports, making it convenient to flush salt, sand, and other
debris from the cooling system.
| Mid Section and Lower Unit |
The mid-section and lower unit of the DF250APX house its most
groundbreaking features. The newly designed low-drag gearcase was
developed specifically to accommodate the Suzuki Selective Rotation
system. While the case itself is actually larger than the previous model
to provide increased gear durability, it is designed with a smoother,
more hydrodynamic shape that allows it to move through the water with
less drag and greater efficiency.
The hallmark feature is Suzuki Selective Rotation, a world-first system
that integrates both regular and counter-rotation operation into a
single lower unit. By changing the gear-shift mode and adding a
counter-rotation propeller, the same outboard can operate in either
direction. In counter-rotation mode, power is transmitted through the
reverse gear, which has been engineered with the same characteristics as
the forward gears.
This is made possible through a special, unified design of gears,
shafts, 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, and are specially heat treated
creating gears that are highly durable.
The lower unit utilizes an aggressive final drive ratio of 2.08:1,
incorporating two-stage gear reduction. This system features a first
stage reduction between the crankshaft and driveshaft, and a second
stage reduction inside the gear case. This design makes a larger gear
ratio possible, allowing it to turn a large 406mm (16-inch) diameter
propeller available in various pitch sizes for optimum performance on a
wide variety of boats. Exhaust is channeled through the propeller hub
for quieter operation.
The Power Trim and Tilt system provides hydraulic control over the
outboard's angle, enabling the operator to adjust the boat's trim for
optimal performance, fuel efficiency, and ride comfort. The system
includes a tilt limit feature that prevents the outboard from tilting
beyond a certain angle to prevent contact with certain boats.
The DF250APX is designed to work with a range of high-performance
stainless steel propellers to match various boat types and load
conditions.
The recommended propeller pitch selection ranges from 15 inches to 27.5
inches for standard rotation models, and from 17 inches to 26 inches for
counter-rotation applications. The robust 2.08:1 gear ratio and the
low-drag gearcase are engineered to effectively transfer the engine's
power to a large 16-inch diameter propeller, optimizing thrust and
overall performance.
The Watergrip Propeller, a stainless steel propeller with a new
interchangeable square-shaped bush, offers efficient conversion of
engine power to propulsion resulting in better grip and performance.
Transom Height (Extra Long Shaft - X): 635 mm (25 in)
Dry Weight (Extra Long Shaft - X): 274-290 kg (603-639 lbs) depending on
model year
Engine Mounting: Shear Mount system
Engine Oil Capacity: 8.0 L (8.5 US qt.) with filter
Recommended Oil: High-quality 4-stroke outboard oil, NMMA FC-W
certified; Ecstar V7000 Synthetic Blend marine oil recommended to
protect V6 internal components
Gearcase Oil Capacity: 1.1 L (1.2 US qt.)
Spark Plugs: NGK BKR6E. Spark Plugs: 25-29 Nm (18-21 lb-ft)
Spark Plug Gap: 0.7-0.8 mm (0.028-0.031 in)
Valve Clearance (Intake): 0.23-0.27 mm (0.009-0.011 in) (cold)
Valve Clearance (Exhaust): 0.33-0.37 mm (0.013-0.015 in) (cold)
Offshore Sports Fishing Boats: Its power, durability, and advanced
features like Selective Rotation for twin installations make it ideal
for offshore center consoles and sportfishing boats, large RIBs (7.5m+),
and heavy-duty commercial vessels. High-Performance Cruisers: Provides
the muscle needed for powering express cruisers, cabin cruisers, and
other large trailerable boats.
Twin and Multi-Engine Installations: The Suzuki Selective Rotation
feature is a significant advantage for multi-engine setups on large
boats, allowing for perfect pairing of standard and counter-rotating
propellers using identical outboards, which helps keep the boat
travelling on an even keel and in a straight line. This eliminates the
need to purchase dedicated counter-rotation models.
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