Suzuki DF25A Specifications
| Engine Model: Suzuki DF25A |
| Engine Type: 4-stroke 3-cylinder SOHC gasoline outboard engine |
| Total Displacement: 29.9 cu.in (490 cc) |
| Rated Engine Power: 25 Hp (18.4 kW) at 6000 rpm |
| Fuel System: Electronic fuel injection |
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The Suzuki DF25A is recognized as one of the
lightest outboards in its class, with a dry weight starting at just 62
kg for the manual start short shaft model. Its groundbreaking
Battery-Less Electronic Fuel Injection system operates without the need
for a battery, an industry first in this Hp class, ensuring reliable
starting and smooth running performance in all conditions while
minimizing weight.
The addition of Suzuki's proven Lean Burn Control technology monitors
engine performance and operating conditions to deliver the optimal
air-fuel mixture, resulting in significant fuel savings and reduced
emissions throughout the operating range. The engine features an offset
crankshaft design, where the crankshaft is positioned slightly off the
center of the cylinder bore to reduce lateral piston pressure, resulting
in smoother operation and greater mechanical efficiency.
Built with Suzuki's advanced anti-corrosion system featuring special
aluminum surface treatment for durability in marine environments, the
DF25A offers user-friendly operation combined with state-of-the-art
engineering. It is an ideal power source for console boats up to
approximately 6 meters, tenders, RIBs, heavy fishing boats, and light
professional workboats.
Engine Model - Suzuki DF25A, DF25AE, DF25AR, DF25AQ, DF25AT, DF25ATH
Engine Type - 4-stroke three-cylinder SOHC gasoline outboard engine
Number of Cylinders - 3 in-line
Displacement - 490 cc (29.9 cu-in)
Cylinder Bore - 60.4 mm (2.38 in)
Piston Stroke - 57.0 mm (2.24 in)
Maximum Engine Power - 18.4 kW (25.0 hp) at 5500 rpm
Full Throttle Operating Range - 5000 - 6000 r/min
Idle Speed - 800 - 900 r/min (850±50)
Compression Ratio - 10.0:1
Fuel System Type - Electronic Fuel Injection with Lean Burn Control
Fuel Pump Type - Integral, battery-less operation
Fuel Type - Unleaded gasoline (87 or 91 octane minimum)
Ignition System - Digital CDI
Cooling System - Water-cooled with thermostat and Fresh Water Flushing
System
Exhaust System - Through propeller hub
Starting System - Manual recoil or electric starter
Choke System - Automatic via EFI system
Throttle Control - Twist grip or remote control
Gear Shift - Forward - Neutral - Reverse
Gear Ratio - 2.09:1
Steering System - Tiller Handle or Remote Control
Trim and Tilt System - Manual (5 tilt pin positions), Gas-Assisted, or
Power Trim/Tilt
Transom Height (Short Shaft) - 381 mm (15 in)
Transom Height (Long Shaft) - 508 mm (20 in)
Trim Angle - 0-16 degrees
Maximum Tilt Angle - 69 degrees
Dry Weight (DF25A, Short Shaft, Manual) - 62-63 kg (137-139 lbs)
Dry Weight (DF25A, Long Shaft, Manual) - 64 kg (141 lbs)
Dry Weight (DF25ATL, Long Shaft, Electric, Power Trim) - 72-73 kg
(159-161 lbs)
Alternator Rating - 12V 14A
The powerhead is constructed around an inline three-cylinder
configuration with a displacement of 490 cc. A notable engineering
feature is the offset crankshaft design, where the crankshaft is
positioned slightly off the center of the cylinder bore. This reduces
the lateral force of the piston against the cylinder wall during the
power stroke, resulting in smoother piston movement and improved
operating efficiency.
The engine mounting utilizes a shear mount design to isolate and dampen
vibration from the hull. The cylinder bore inside diameter measures
60.400-60.415 mm, with a maximum permissible out-of-round of 0.050 mm.
The piston skirt diameter is 60.365-60.380 mm, resulting in a
piston-to-cylinder clearance of 0.0271-0.0425 mm. The piston pin outside
diameter is 15.995-16.000 mm, with a piston pin bore inside diameter of
16.002-16.008 mm, providing a clearance of 0.002-0.013 mm. The
connecting rod big end inside diameter is 29.025-29.034 mm, with a crank
pin outside diameter of 28.989-29.000 mm, resulting in an oil clearance
of 0.025-0.049 mm.
Connecting rod side clearance at the big end is 0.100-0.250 mm. The
crankshaft journal outside diameter is 31.986-32.000 mm with an oil
clearance of 0.020-0.051 mm. Maximum crankshaft runout is 0.040 mm. The
piston rings include a top ring, second ring, and oil ring. The top ring
has a width of 1.02-1.04 mm and an end gap of 0.12-0.25 mm. The second
ring width is 1.21-1.23 mm with an end gap of 0.26-0.39 mm. Top ring
side clearance is 0.030-0.070 mm, while second ring side clearance is
0.02-0.06 mm.
The cylinder head incorporates a Single OverHead Camshaft (SOHC) valve
train with four valves per cylinder, two intake and two exhaust. The
DF25A is the first in its class to feature friction-reducing roller
rocker arms. The SOHC is mounted over the cylinder head and driven by
the crankshaft through a timing belt. The cylinder head warp limit is
0.050 mm. Intake valve head diameter is 29.0 mm, and exhaust valve head
diameter is 26.0 mm.
Minimum valve head thickness for both valves is 0.50 mm. The intake
valve stem outside diameter is 4.975-4.990 mm, while the exhaust valve
stem is 4.955-4.970 mm. Valve guide inside diameter for both valves is
5.000-5.012 mm. Intake valve stem-to-guide clearance is 0.010-0.037 mm,
and exhaust clearance is 0.030-0.057 mm. Valve seat width for both
intake and exhaust is 0.9-1.1 mm.
The valve spring free length is 34.29 mm. Intake cam height is
25.430-25.490 mm, and exhaust cam height is 25.140-25.200 mm. Camshaft
journal outside diameter is 24.959-24.980 mm for the upper journal,
34.450-34.475 mm for the center journal, and 22.959-22.980 mm for the
lower journal, with an oil clearance of 0.020-0.062 mm. Valve lash is
set to 0.18-0.22 mm for intake valves and 0.20-0.24 mm for exhaust
valves.
The DF25A features a revolutionary Multi-Point Sequential Electronic
Fuel Injection system that operates without a battery, an industry first
in this Hp class. All-new components were designed to be as compact and
lightweight as possible, including an inline high-pressure fuel pump,
fuel injectors, and a new throttle body. The system provides quicker
starts, smoother running performance, and superior acceleration in all
operating conditions.
Suzuki's Lean Burn Control technology predicts fuel requirements based
on operating conditions and delivers the optimal air-fuel mixture to the
engine, resulting in remarkable fuel economy throughout the operating
range. A standard 25-liter external fuel tank is included with the
engine. The engine is designed to run on unleaded gasoline with a
minimum octane rating of 87 or 91.
The lubrication system is a pressure-fed wet sump design utilizing a
trochoid-type cam-driven oil pump to ensure reliable oil delivery to all
critical engine components. This pressurised system reduces friction and
wear, enhancing engine longevity. The engine includes a replaceable
cartridge-style oil filter.
The oil filter mounting bolt torque is 14 Nm (10.5 lb-ft). An oil
pressure regulator is set to 27 Nm (19.5 lb-ft). Engine oil capacity is
1.50 liters of SAE 10W-30 or 10W-40 oil, meeting API service
classifications SG through SM. A low oil pressure warning system with
LED indicator protects the engine from operation with insufficient oil
pressure.
Engine temperature is regulated by a water-cooled system with a
thermostat. Cooling water is drawn into the engine through intakes on
the gearcase and circulated by a rubber impeller water pump. A
thermostat maintains optimal operating temperature for combustion
efficiency and performance.
The Fresh Water Flushing System allows owners to easily flush cooling
passages with fresh water after use in salt or polluted water. An
overheat warning system alerts the operator to cooling system
malfunctions. A tell-tale port provides visible confirmation that the
cooling system is operational.
| Mid Section and Lower Unit |
The mid-section houses the driveshaft and provides the mounting
interface to the transom bracket via the engine mounting system. The
lower unit contains the gearcase, which is filled with 0.33 liters of
Suzuki Outboard Motor Gear Oil or GL5 SAE 90 gear oil.
The gears provide a reduction ratio of 2.09:1, optimizing propeller
speed for effective thrust. The shift mechanism enables smooth and
positive engagement of Forward, Neutral, and Reverse gears. Exhaust
gases are expelled through the propeller hub for quieter operation.
Trim and tilt adjustments are available in several configurations
depending on model selection: manual with 5 tilt pin positions,
gas-assisted, or fully electric power trim and tilt. The manual tilt
system uses a pin in one of five adjustment positions on the transom
bracket.
Power trim models provide smooth tilting of the outboard with greater
convenience and improved easier operation. A tilt release lever on
manual models disengages the lock for tilting the engine out of the
water for beaching, trailering, or storage. Shallow water drive settings
are available for operation in minimal water depths. The trim angle
range is 0-16 degrees, with a maximum tilt angle of 69 degrees.
The DF25A is designed to use three-bladed aluminum propellers with a
spline drive rubber hub. The standard propeller diameter is 260 mm
(10.25 in). A wide range of propeller pitches is available from 9 inches
to 15 inches to accommodate different boat and loading conditions.
Available propeller pitches include 9, 10, 11, 12, 13, 14, and 15
inches. The standard propeller supplied is a 3 x 9.25 x 10 configuration
for manual start models. Selecting the correct pitch is crucial for
allowing the engine to operate within its recommended full-throttle RPM
range of 5000-6000 for optimal performance and efficiency.
The overall length varies by configuration: 695.0 mm (27.4 in) for
DF25A, 645.0 mm (25.4 in) for DF25AR, and 673.0 mm (26.5 in) for DF25AT.
Overall width is 395.0 mm (15.5 in). The short shaft model, designed for
a 381 mm (15 in) transom, has an overall height of 1230.0 mm (48.4 in).
The long shaft model, for a 508 mm (20 in) transom, has an overall
height of 1355.0 mm (53.4 in).
The manual start short shaft model has a dry weight of 62-63 kg (137-139
lbs) depending on configuration. The manual start long shaft model
weighs 64 kg (141 lbs). Electric start remote control models with power
trim and tilt range from 72-75 kg (159-165 lbs) depending on shaft
length.
Every 100 hours of operation or annually, the following tasks should be
performed: change engine oil, change gear oil, check and clean the spark
plug (adjusting the gap to 0.8-0.9 mm), inspect the fuel line and
breather for leaks or cracks, check the low pressure fuel filter,
inspect the condition of the sacrificial anodes, verify thermostat
operation, and check the propeller nut and cotter pin. On electric start
models, the battery should also be checked.
Every 200 hours, in addition to the 100-hour checks, the engine requires
replacement of the oil filter, inspection and adjustment of valve lash,
inspection of the timing belt, checking and adjusting the idle speed,
inspecting the water pump and its impeller, checking the water pump
impeller, and checking the air cleaner element.
Every 300 hours, the spark plugs should be replaced with NGK CPR6EA-9 ,
and the water pump impeller must be replaced to prevent cooling system
failure. Every 400 hours, the in-line fuel filter should be replaced.
Every 1000 hours, the low pressure pump filter should be checked.
Engine oil capacity is 1.50 liters of SAE 10W-30 or 10W-40 oil meeting
API SG through SM. Gearcase capacity is 0.33 liters of Suzuki Outboard
Motor Gear Oil or GL5 SAE 90. Spark plug type is NGK CPR6EA-9 with a gap
of 0.8-0.9 mm. Spark plug tightening torque is 10-12 Nm (7.5-9.0 lb-ft).
Valve lash is 0.18-0.22 mm for intake and 0.20-0.24 mm for exhaust.
Ignition timing is 7-25 degrees BTDC.
Cylinder head bolt - 30 Nm (21.7 lb-ft)
Cylinder head cover bolt - 10 Nm (7.2 lb-ft)
Crankcase bolts (inside) - 28 Nm (21.0 lb-ft)
Crankcase bolts (outside) - 11 Nm (8.0 lb-ft)
Connecting rod cap bolt - 10 Nm (7.2 lb-ft)
Flywheel nut - 100 Nm (75.5 lb-ft)
Camshaft pulley bolt - 30 Nm (22.0 lb-ft)
Crankshaft timing pulley nut - 50 Nm (36.0 lb-ft)
Rocker arm shaft bolt - 6 Nm (4.4 lb-ft)
Valve adjusting screw lock nut - 10 Nm (8.0 lb-ft)
Intake manifold bolt/nut - 23 Nm (16.5 lb-ft)
Oil pressure regulator - 27 Nm (19.5 lb-ft)
Throttle body - 11 Nm (8.0 lb-ft)
Low pressure fuel pump bolt - 11 Nm (8.0 lb-ft)
Starter motor mounting bolt - 23 Nm (16.5 lb-ft)
Oil pump bolt - 11 Nm (8.0 lb-ft)
Engine oil filter - 14 Nm (10.5 lb-ft)
Water pump case nut - 6 Nm (4.3 lb-ft)
Power unit mounting bolt - 23 Nm (16.5 lb-ft)
Driveshaft housing bolt - 23 Nm (16.5 lb-ft)
Propeller nut - 25 Nm (18.0 lb-ft)
Gearcase bolt - 23 Nm (16.5 lb-ft)
Tiller handle bolt - 23 Nm (16.5 lb-ft)
Spark plug - 10-12 Nm (7.5-9.0 lb-ft)
The Suzuki DF25A is engineered for a wide variety of watercraft
applications. Its compact size, light weight, and advanced features make
it an ideal primary power source for console boats up to approximately 6
meters, tenders, RIBs, heavily loaded fishing boats, and inflatable
craft with extra equipment. It is suitable for recreational boaters and
anglers seeking an efficient, quiet, and reliable outboard for various
water conditions.
The engine is also a popular and dependable choice as an auxiliary motor
for sailboats and for light professional use in workboats. The engine is
saltwater rated and suitable for use in both freshwater and saltwater
environments when properly maintained, featuring Suzuki's special
anti-corrosion treatment to protect against corrosive elements such as
saltwater. The DF25A meets international emission standards.
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