Yanmar 3T75U Specifications
| Engine Model: Yanmar 3T75U |
| Engine Type: 4-stroke 3-cylinder naturally aspirated water-cooled diesel |
| Total Displacement: 60.7 cu.in (0.99 L) |
| Rated Engine Power: 20 Hp (14.9 kW) at 2400 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 3T75U is a 1.0-liter,
three-cylinder, naturally aspirated diesel engine produced from the
early 1980s through the mid-1990s. It was developed as a compact and
efficient powerplant for Yanmar’s compact tractor range, primarily
serving models such as the YM1610, YM1702, YM1720, and the F series
tractors including the F16D. The “U” designation in the engine code
refers to its specific configuration for utility tractor applications,
distinguishing it from industrial or marine variants within the 3T
engine family.
The engine’s architecture is defined by its vertical three-cylinder
layout, indirect injection combustion system, and liquid-cooled design -
features selected to deliver reliable low-speed torque for agricultural
tasks including tilling, mowing, and light material handling. The Yanmar
3T75U’s reputation within the compact tractor community is one of
durability and fuel efficiency, with many units remaining in service
decades after production ceased, supported by a continuing availability
of service parts through aftermarket channels.
The 3T75U engine embodies Yanmar’s engineering philosophy for small
agricultural diesels, prioritizing reliability, smooth operation, and
serviceability within a compact package. The engine’s 1.0-liter
displacement is achieved through a square bore and stroke configuration
of 75 mm x 75 mm, providing balanced power delivery across the operating
range. The three-cylinder inline layout produces a firing interval of
240 degrees of crankshaft rotation, resulting in smoother operation than
single or twin-cylinder alternatives while maintaining a narrower engine
width suitable for compact tractor chassis packaging.
The indirect injection combustion system, utilizing a swirl chamber
design, delivers quiet operation and reduced mechanical stress on the
rotating assembly compared to direct injection engines of the same era.
The cylinder block is manufactured from cast iron with replaceable
cylinder liners, enabling in-frame overhauls without complete engine
removal - a serviceability feature valued by equipment owners in
agricultural settings.
The engine’s power output ranges from 16 to 20 horsepower depending on
the specific application and tractor model, with rated speeds between
2,400 and 2,600 rpm. The 3T75U’s mechanical fuel system, featuring a
Bosch-type inline injection pump, provides reliable starting and speed
regulation under varying loads encountered in PTO-driven implements and
field operations.
Production Period: 1982 - 1995
Engine Code: 3T75U
Configuration: Inline three-cylinder (I3)
Displacement: 0.994 L (60.7 cu.in)
Bore: 75.0 mm (2.95 in)
Stroke: 75.0 mm (2.95 in)
Firing Order: 1-2-3
Compression Ratio: 23.0:1
Combustion System: Indirect injection (swirl chamber type)
Aspiration: Naturally aspirated
Valvetrain: OHV (Overhead Valve), 6 valves (2 per cylinder)
Rotation Direction: Counter-clockwise
Max Power (YM1610): 16 hp (11.9 kW) @ 2,400 rpm
Max Power (YM1720): 17 hp (12.7 kW) @ 2,400 rpm
Max Power (F16D / YM1610D): 20 hp (14.9 kW)
Peak Torque: 62-69 Nm (46-51 lb-ft) @ 1,800-2,000 rpm
The 3T75U cylinder block is manufactured from high-strength cast iron,
utilizing a deep-skirt design that extends below the crankshaft
centerline to provide rigidity and reduce vibration transmission. The
inline three-cylinder configuration with a square 75 mm x 75 mm bore and
stroke yields a displacement of 994 cc - a design that optimizes bore
surface area relative to combustion chamber volume for efficient thermal
transfer. The block features an open-deck design at the top of the
cylinder bores.
Four main bearings support the forged steel crankshaft. Replaceable
dry-type or wet-type cylinder liners are inserted into the block
depending on the specific variant, allowing for in-frame overhauls.
Cast-in coolant passages surround each cylinder bore, while oil
galleries are drilled into the block to supply pressurized lubricant to
the crankshaft, connecting rods, and cylinder head. The engine mounting
points are cast into the block to accommodate the longitudinal
orientation used in Yanmar compact tractors.
0The cylinder head is manufactured from cast iron and features an
overhead valve (OHV) arrangement with two valves per cylinder - one
intake and one exhaust - for a total of six valves. The camshaft is
positioned within the cylinder block and operates the valves through
mechanical pushrods and rocker arms. Valve lash is adjustable using a
screw-and-locknut mechanism on the rocker arms. The specified cold valve
clearance range is 0.15 mm to 0.20 mm (0.006 to 0.008 in) for both
intake and exhaust valves.
The cylinder head incorporates the indirect injection system’s swirl
chambers, where fuel is injected and initial combustion occurs before
the burning mixture expands into the main cylinder. This pre-chamber
design contributes to smooth combustion, reduced noise, and lower
mechanical stress. The cylinder head gasket is a composite construction
designed to withstand the 23.0:1 compression ratio.
The fuel system utilizes a mechanical indirect injection system with a
Bosch-type inline injection pump mounted on the side of the engine. The
injection pump is driven by the engine’s gear train and incorporates a
mechanical governor to maintain consistent engine speed under varying
loads - a feature critical for PTO-driven agricultural implements.
High-pressure injection lines deliver fuel to the injection nozzles
located in each cylinder head’s swirl chamber. The specified fuel
injection pressure is 160-170 kg/cm2 (2,275-2,418 psi). The injection
timing is set to 20°-21° before top dead center. A mechanical feed pump
draws fuel from the tank and delivers it through a fuel filter equipped
with a water separator.
The lubrication system employs a wet-sump design with a trochoid-type
oil pump. The pump draws oil from the sump through a screened pickup
tube and delivers it through a full-flow spin-on oil filter. The
filtered oil is distributed through internal galleries to the crankshaft
main bearings, connecting rod bearings, camshaft bearings, and the
rocker arm assembly.
A pressure relief valve is integrated into the oil pump assembly. Total
system capacity is 3.0 to 3.5 liters (3.2 to 3.7 qt). The recommended
oil viscosity grades are SAE 10W-30, 10W-40, or 15W-40, with API
classification appropriate for diesel engines of the era. The compatible
oil filter element is UNION JO-180 or equivalent.
The cooling system is a pressurized water-cooled design utilizing a
crossflow radiator. A centrifugal water pump, driven by the accessory
drive belt, circulates coolant through the cylinder block, cylinder
head, and radiator. A wax-element thermostat is positioned in the
coolant outlet housing to regulate coolant flow and maintain the engine
within its optimal operating temperature range.
The system incorporates an expansion tank to accommodate coolant
expansion and to facilitate air removal. An engine-driven fan provides
airflow across the radiator. Total coolant capacity is 4.0 liters (4.2
qt), with the system capacity varying by radiator size and
configuration.
| Intake and Exhaust Systems |
Intake System: The intake system consists of an air cleaner housing with
a replaceable dry-type filter element, ducting to the intake manifold,
and the intake manifold itself, which is constructed from cast iron. The
manifold is designed with runners that distribute intake air evenly to
each cylinder.
Exhaust System: The exhaust system utilizes a cast iron exhaust manifold
designed to withstand thermal cycling. The manifold directs exhaust
gases through a vertical exhaust stack or under-chassis exhaust routing
depending on the tractor configuration.
Electrical System: The engine is equipped with a 12-volt electrical
system. The starter motor is a 1.0 kW or 1.2 kW electric starter with a
reduction-gear design. The alternator provides charging current for the
battery and vehicle electrical loads.
Starting System: Glow plugs are installed in the cylinder head to assist
with cold starting, with a glow plug control timer managing pre-heat
duration based on ambient temperature.
Cold Start Aid: The indirect injection system features glow plugs in
each swirl chamber. The glow plug circuit is activated by a key-switch
position, with a visual indicator (glow plug light) on the instrument
panel signaling when the cylinders are adequately pre-heated.
0Overall Length: 550 mm (21.7 in)
Overall Width: 450 mm (17.7 in)
Overall Height: 600 mm (23.6 in)
Dry Weight (complete engine): 90-100 kg (198-220 lb)
Engine Oil: SAE 10W-30, 10W-40, or 15W-40 meeting API CD, CE, CF, or
higher
Oil Capacity (with filter change): 3.0-3.5 L (3.2-3.7 qt)
Oil Change Interval: 100-150 hours of operation
Fuel Filter: Replace at 200-250 hours
Coolant Capacity: 4.0 L (4.2 qt) (engine and radiator, approximate)
Intake Valve Clearance (Cold): 0.15-0.20 mm (0.006-0.008 in)
Exhaust Valve Clearance (Cold): Intake: 0.15-0.20 mm (0.006-0.008 in)
Engine Idle Speed: 750-850 rpm
Rated Engine Speed: 2,400-2,600 rpm
Fuel Injection Pressure: 160-170 kg/cm2 (2,275-2,418 psi)
Injection Timing: 20°-21° BTDC
0Cylinder Head Bolts, Stage 1: 39.3 Nm (29 lb-ft)
Cylinder Head Bolts, Stage 2: 78 Nm (58 lb-ft)
Cylinder Head Bolts, Stage 3 (final): 97-107 Nm (72-79 lb-ft)
Cylinder Head Assist Bolts: 30 Nm (22 lb-ft)
Connecting Rod Cap Nuts: 50-55 Nm (37-41 lb-ft)
Main Bearing Cap Bolts: 55-60 Nm (41-44 lb-ft)
Flywheel Bolts: 70-80 Nm (52-59 lb-ft)
Injector Holders: 50-60 Nm (37-44 lb-ft)
Glow Plugs: 15-20 Nm (11-15 lb-ft)
Rocker Arm Shaft Brackets: 20-25 Nm (15-18 lb-ft)
Intake Manifold to Cylinder Head: 20-25 Nm (15-18 lb-ft)
Exhaust Manifold to Cylinder Head: 20-25 Nm (15-18 lb-ft)
Yanmar Compact Tractors
YM Series: YM1610, YM1610D, YM1601, YM1602D.
YM Series: YM1702, YM1702D, YM1720, YM1720D.
YM Series: YM1802, YM1802D, YM1810.
F Series: F16D, F14D, F15, F165, F175.
Ke Series: Ke-1, Ke-2, Ke-3, Ke-4 (selected variants).
Grey Market Tractors (Various Imported Models): The 3T75U engine appears
in numerous grey market Yanmar tractors imported from Japan to North
America, Europe, and Australia. Model designations may vary by importer
and region, with common variants including the 3T75U-NC (for F16D) and
3T75U-NA (for YM1702D and YM1720D).
Parts Compatibility: The 3T75U shares many internal components with the
3T72 engine (72 mm bore), including main bearings, connecting rod
bearings, and piston rings. The engine is part of Yanmar’s 3T family,
which includes the 3T72, 3T75, and 3T84 variants.
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