Suzuki DF40ATL Specifications
| Engine Model: Suzuki DF40ATL |
| Engine Type: 4-stroke 3-cylinder long shaft gasoline outboard engine |
| Total Displacement: 57.4 cu.in (941 cc) |
| Rated Engine Power: 40 Hp (29.5 kW) at 6000 rpm |
| Fuel System: Multi-point sequential electronic fuel injection |
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The Suzuki DF40ATL is a 40.0 Hp, four-stroke
outboard engine. It utilizes a three-cylinder in-line configuration with
a Double Overhead Camshaft (DOHC) and 12 valves. The engine displacement
is 57.4 cubic in (941 cc), achieved through a cylinder bore of 2.85 in
(72.5 mm) and a piston stroke of 2.99 in (76.0 mm). This powerhead is
designed to operate at a maximum engine speed range of 5000 to 6000 rpm
and maintains an idle speed of 800 ±50 rpm.
The compression ratio is specified at 9.7:1. Lubrication is managed by a
wet sump system utilizing a trochoid oil pump. The engine features a
through-propeller exhaust system and is cooled by a water-cooled,
thermostat-controlled system. Ignition is handled by a
full-transistorized system, and starting is accomplished via an electric
starter. The 12-volt electrical system is supported by a charging
alternator rated at 19 amperes.
The cylinder block houses precision-machined bores with an inside
diameter of 2.8543-2.8551 in (72.500-72.520 mm). The maximum permissible
out-of-round for a cylinder bore is 0.002 in (0.050 mm). The crankshaft
features journal outside diameters of 1.7709-1.7717 in (44.982-45.000
mm), with an oil clearance of 0.0006-0.0013 in (0.014-0.034 mm).
Crankpin outside diameter is 1.4954-1.4961 in (37.982-38.000 mm).
Connecting rod big end inside diameter measures 1.6142-1.6149 in
(41.000-41.018 mm), with an oil clearance of 0.0012-0.0019 in
(0.031-0.049 mm) and a side clearance of 0.0039-0.0098 in (0.100-0.250
mm). Pistons have a skirt diameter of 2.8531-2.8539 in (72.470-72.490
mm), resulting in a piston-to-cylinder clearance of 0.0008-0.0016 in
(0.020-0.040 mm).
Piston pin outside diameter is 0.7085-0.7087 in (17.995-18.000 mm).
Piston ring specifications include top and second ring widths and end
gaps, with top ring end gap at 0.0059-0.0118 in (0.15-0.30 mm) and
second ring end gap at 0.0118-0.0177 in (0.30-0.45 mm). Ring side
clearances are also specified, with the top ring at 0.0012-0.0028 in
(0.030-0.070 mm).
The cylinder head has a maximum warp limit of 0.002 in (0.050 mm).
Intake valves feature a head diameter of 1.05 in (26.6 mm), while
exhaust valves are 0.85 in (21.5 mm) in diameter. Intake valve stem
outside diameter is 0.2152-0.2157 in (5.465-5.480 mm), and exhaust valve
stem diameter is 0.2142-0.2148 in (5.440-5.455 mm). Corresponding valve
guide inside diameters are 0.2165-0.2170 in (5.500-5.512 mm) for both
intake and exhaust.
This yields a stem-to-guide clearance of 0.0008-0.0019 in (0.020-0.047
mm) for intake valves and 0.0018-0.0028 in (0.045-0.072 mm) for exhaust
valves. Valve seat width is maintained at 0.043-0.051 in (1.1-1.3 mm)
for both intake and exhaust. The valve spring free length is 1.30 in
(33.10 mm).
Camshaft intake lobe height is 1.5039-1.5102 in (38.200-38.360 mm), and
exhaust lobe height is 1.4858-1.4921 in (37.740-37.900 mm). Camshaft
journal outside diameter measures 0.9029-0.9037 in (22.934-22.955 mm),
with a corresponding housing inside diameter of 0.9055-0.9063 in
(23.000-23.021 mm), resulting in an oil clearance of 0.0018-0.0034 in
(0.045-0.087 mm).
Fuel delivery is managed by a multi-point sequential electronic fuel
injection system. An integral fuel pump is incorporated within the
system. The engine is designed to operate on unleaded gasoline with a
minimum octane rating of 87. An optional 6.6-gallon (25.0-liter)
portable fuel tank is available for this model.
| Gear Housing and Lower Unit |
Power transfer to the propeller is managed through a bevel gear
reduction system with a published gear ratio of either 2.28:1 or 2.27:1
depending on the data source. The gearbox utilizes a dog clutch for
forward, neutral, and reverse gear engagement. The gearcase has a
lubricant capacity of 0.65 quarts (0.61 liters).
| Mid Section and Trim System |
The engine is equipped with a power trim and tilt system, allowing for
trim angle adjustment from 0 to 19 degrees and a maximum tilt angle of
72 degrees. The DF40ATL model is configured for remote steering,
utilizing a shear mount for engine isolation.
The engine is designed to operate with a range of three-bladed aluminum
propellers. Available diameters include 11.25 in (285 mm) and 11.5 in
(292 mm). A wide selection of pitches is offered, ranging from 9 in (228
mm) to 17 in (432 mm), allowing for fine-tuning to specific boat and
load conditions.
Two primary variants of this engine exist, differing in overall length
due to steering configuration. The DF40ATL model, designed for remote
steering, has an overall length of 27.5 in (699.0 mm). The tiller-handle
version, the DF40ATHL, extends to 32.0 in (814.0 mm) in overall length.
Both models share an overall width of 14.8 in (377.0 mm).
For the long shaft version, the overall height is 54.6 in (1385.0 mm),
which corresponds to a transom height of 20 in (508 mm). The dry weight
for the DF40ATL long shaft model is 229.0 lbs (104.0 kg), while the
tiller-handle DF40ATHL is slightly heavier at 238.0 lbs (108.0 kg).
Engine lubrication requires 2.85 quarts (2.70 liters) of SAE 10W-30 or
10W-40 oil meeting API service classifications SG, SH, SJ, SL, or SM.
The gearcase requires Suzuki Outboard Motor Gear Oil or GL5 SAE 90
lubricant, with a capacity of 0.64 quarts (0.61 liters).
The ignition timing is set at 2-22 degrees before top dead center.
Recommended spark plugs are NGK DCPR6E, gapped to 0.031-0.035 in
(0.8-0.9 mm). Valve lash, when cold, should be set to 0.007-0.009 in
(0.18-0.22 mm) for intake valves and 0.011-0.013 in (0.28-0.32 mm) for
exhaust valves.
Routine checks, including the battery, engine oil, gear oil, spark
plugs, fuel lines, anodes, and thermostat, are recommended every 100
hours of operation. More extensive maintenance, such as replacing the
oil filter, checking valve lash, inspecting the timing belt, and
servicing the water pump, is advised every 200 hours. Spark plug
replacement and water pump impeller replacement are scheduled for every
300 hours. The low-pressure fuel filter should be replaced at 400-hour
intervals.
The cylinder head bolts are torqued to 59 Nm (42.7 lb-ft). Connecting
rod cap bolts require 15 Nm (11.0 lb-ft). The flywheel nut is a
high-torque fastener at 166 Nm (120.0 lb-ft). The cylinder head cover
and camshaft housing bolts are secured to 11 Nm (8.2 lb-ft). Crankcase
bolts vary, with inside bolts at 46 Nm (33.5 lb-ft) and outside bolts at
25 Nm (18.0 lb-ft).
Intake manifold bolts and nuts are torqued to 23 Nm (16.5 lb-ft). The
propeller nut is tightened to 55 Nm (40.0 lb-ft). Spark plugs require
10-12 Nm (7.5-9.0 lb-ft). The engine oil filter is installed at 14 Nm
(10.5 lb-ft). Power unit and driveshaft housing mounting bolts are
torqued to 50 Nm (36.0 lb-ft). Gearcase bolts are set at 23 Nm (16.5
lb-ft).
The Suzuki DF40ATL is a versatile outboard suited for a wide array of
small to medium-sized marine craft. Its 20-inch long shaft makes it
ideal for boats with a standard transom height, including rigid
inflatable boats (RIBs), aluminum fishing boats, small center consoles,
skiffs, and pontoon boats.
The engine's combination of power, fuel efficiency from its Lean Burn
Control System, and relatively light weight allows it to serve as a
primary power source for vessels up to approximately 4.2 meters in
length and as a reliable auxiliary or kicker motor for larger craft
where precise trolling speeds are desired, optionally aided by the Troll
Mode System. The remote steering configuration of the ATL model
integrates seamlessly with center console or side console layouts.
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