Yanmar 3JH2E Specifications
| Engine Model: Yanmar 3JH2E |
| Engine Type: 4-stroke inline 3-cylinder naturally aspirated water-cooled diesel |
| Total Displacement: 83.2 cu.in (1.36 L) |
| Rated Engine Power: 38 Hp (28.5 kW) at 3600 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 3JH2E is a 1.4-liter, naturally
aspirated, three-cylinder marine diesel engine manufactured by Yanmar.
This powerplant belongs to the JH2 series, a platform engineered
specifically for sailboat auxiliary propulsion and small to mid-sized
displacement vessels. The 3JH2E has gained recognition for its compact
dimensions, low vibration operation, and fuel efficiency in marine
environments.
The engine operates on a four-stroke, compression-ignition cycle with a
vertical, water-cooled inline configuration. The indirect injection
system utilizes a swirl pre-combustion chamber to reduce combustion
noise and provide smooth operation at low engine speeds, a valuable
characteristic for auxiliary engines on sailing yachts. Yanmar
engineered the 3JH2E with a constant high-temperature fresh water
cooling system with a heat exchanger, isolating the engine block from
corrosive seawater while maintaining stable operating temperatures.
The engine carries a counterclockwise crankshaft rotation when viewed
from the flywheel end, translating to clockwise propeller rotation when
viewed from the stern for standard transmission configurations. The
3JH2E is found in sailboats, small fishing vessels, and workboats
requiring a reliable 35 to 38 horsepower auxiliary power source.
The Yanmar 3JH2E is a four-stroke, compression-ignition, inline
three-cylinder diesel engine with vertical cylinder arrangement. The
induction system is naturally aspirated without turbocharging equipment.
Total displacement measures 1,363 cc, equivalent to 83.2 cubic inches.
The bore dimension is 82 mm (3.23 in), and the stroke dimension is 86 mm
(3.39 in). The compression ratio is not published in the available
service data. The firing order sequence is 1-3-2.
Maximum power output reaches 28.5 kW, equivalent to 38 hp, at an engine
speed of 3,600 rpm. Continuous power output is 25.7 kW, equivalent to 35
hp, at an engine speed of 3,400 rpm. Maximum torque is 78.5 Nm,
equivalent to 58.0 lb-ft, at an engine speed of 3,000 rpm. The
combustion system is indirect injection with a swirl pre-combustion
chamber. Fuel injection timing is set at 14 degrees before top dead
center (BTDC). Fuel injection pressure is 19.6 MPa, equivalent to 200
kg/cm2.
The cylinder block is constructed from cast iron, providing rigidity,
vibration damping, and wear resistance required for prolonged marine
service. The block is an inline three-cylinder design with integral
cylinder bores. A four-main-bearing crankshaft support structure is
employed, with three connecting rod journals positioned between four
main bearings.
The deep-skirt block design contributes to structural rigidity and noise
reduction. The water jacket surrounds the entirety of the cylinder bores
to maximize heat transfer away from the combustion zone. The block
includes the timing gear housing at the front, containing the gear train
that drives the camshaft, injection pump, and oil pump.
The cylinder head is a separate cast-iron component bolted to the top of
the cylinder block using a single-piece head gasket. The cylinder head
contains two valves per cylinder, one intake and one exhaust, for a
total of six valves. The combustion chamber is formed partly in the
cylinder head as a swirl pre-combustion chamber and partly in the piston
crown. This swirl chamber design produces intense air rotation during
the compression stroke, promoting complete mixing of fuel and air before
ignition.
The valvetrain is an overhead valve (OHV) configuration with pushrods
actuated by the camshaft located within the cylinder block. Valve lash
adjustment is performed via set screws on the rocker arms. Cold valve
clearance specification for both intake and exhaust valves is 0.20 mm
(0.008 in). The cylinder head assembly includes valve seats, valve
guides, rocker arm shaft, rocker arms, and valve springs.
The fuel system employs a mechanical indirect injection design with a
swirl pre-combustion chamber. The injection pump is a distributor-type
or in-line pump depending on the specific variant. The pump is mounted
on the side of the cylinder block and driven by a gear train from the
camshaft. A mechanical governor controls engine speed, sensing engine
rpm and adjusting fuel delivery to maintain the selected speed under
varying loads.
A fuel feed pump mounted on the injection pump housing draws fuel from
the tank through a primary filter and water separator. The injection
pump pressurizes fuel to 200 kg/cm2 (2,845 psi) and delivers it to
individual injection lines. These steel lines carry high-pressure fuel
to the injection nozzles mounted in the cylinder head. Each nozzle
directs fuel into the swirl pre-combustion chamber, where initial
combustion begins.
The burning gases then expand through a throat into the main cylinder.
This two-stage combustion process reduces peak cylinder temperatures and
pressures, lowering NOx emissions and combustion noise. A manual shutoff
lever on the injection pump or a solenoid-operated stop device provides
engine stopping.
The lubrication system is a forced lubrication design with a trochoid
pump. The oil pump is driven directly by a gear on the crankshaft or
camshaft. A suction pipe extends from the pump into the oil sump,
drawing oil through a wire-mesh strainer. After pressurization, oil
passes through a full-flow oil filter mounted externally on the cylinder
block. From the filter, oil travels through internal drillings to reach
the main bearings. Drilled passages within the crankshaft direct oil
from the main bearings to the connecting rod bearings.
Excess oil is directed upward through vertical passages to lubricate the
valve train. The system capacity is 5.0 liters (5.3 US qt) total,
including the oil filter. Operating oil pressure at maximum engine
output (3,600 rpm) should register 340 kPa to 440 kPa (49 psi to 64
psi), equivalent to 3.5 to 4.5 kg/cm2. A pressure relief valve located
near the oil pump outlet prevents excessive pressure during cold starts.
Recommended oil viscosity is SAE 15W-40 with API service classification
CD or higher.
The cooling system is an indirect freshwater cooling system with a heat
exchanger. This marine-specific design uses two separate water circuits.
The primary circuit contains fresh water mixed with coolant additive,
circulating through the engine block, cylinder head, and the tube side
of the heat exchanger. A centrifugal water pump driven by the engine
circulates the fresh water. The secondary circuit draws raw water
(seawater or fresh water) through a sea strainer.
A flexible-impeller raw water pump pumps the raw water through the shell
side of the heat exchanger, where it absorbs heat from the engine
coolant before being discharged overboard. This system isolates the
engine's internal passages from corrosive seawater. A wax-type
thermostat regulates the fresh water temperature. The engine-only
cooling capacity is not specified, but the total system with the heat
exchanger and external piping is sized for continuous marine duty.
Electrical System: The electrical system is 12-volt with negative
ground. A starter motor rated at 1.4 kW engages with the flywheel ring
gear. A belt-driven alternator is available in 55 ampere or 80 ampere
ratings depending on the production year and specification.
Sheathed-type glow plugs provide cold starting assistance. One glow plug
is installed in each swirl pre-combustion chamber.
Air Intake System: Air enters through a dry-type air cleaner with a
paper filter element. The intake manifold is a cast-iron component
distributing air evenly to all three cylinders.
Exhaust System: Exhaust gases exit each cylinder into the exhaust
manifold, then pass through a water-cooled mixing elbow where raw water
is injected to cool the exhaust gases before entering the exhaust hose.
Transmission: The engine is paired with either a KM3A cone clutch
transmission or a KBW10E multiple friction disc transmission depending
on the application. The KM3A is a mechanical cone clutch type with a
downward angle of 7 degrees. Forward reduction ratios are 2.36:1 or
2.61:1 depending on the specific gear set. Reverse reduction ratio is
3.16:1. The KBW10E is a constant mesh, multiple friction disc type with
SAE 5 mounting flange. Gear oil capacity for the KM3A is 0.45 liters
(0.48 US qt) of SAE 15W-40. The KBW10E requires 0.7 liters (0.74 US qt)
of ATF Type "A".
The complete engine assembly, including the injection pump, heat
exchanger, alternator, starter, and flywheel housing, has an overall
length of 782 mm (30.8 in), a width of 511 mm (20.1 in), and a height of
587 mm (23.1 in). The dry weight, excluding fluids but including all
standard engine-mounted accessories and the flywheel housing, is 165 kg
(364 lb). With the KM3A transmission attached, the dry weight is 186 kg
(410 lb).
Service intervals for the 3JH2E are based on operating hours. Engine oil
and filter should be changed every 150 hours under normal conditions.
For a new engine or after major overhaul, change the oil after the
initial 50 hours of operation. Oil viscosity selection follows SAE
15W-40 with API service classification CD or higher. The fuel filter
requires replacement every 250 hours.
The air cleaner element requires cleaning every 100 hours and
replacement every 500 hours. Valve lash adjustment is required every 250
hours. The cooling system requires testing of coolant freeze point and
corrosion inhibitor level every 250 hours. Complete coolant replacement
occurs every 1,000 hours or one year. The raw water pump impeller
requires inspection every 200 hours and replacement every 500 hours.
Fuel injection timing should be checked every 1,000 hours. The fuel
injectors require testing and recalibration every 1,000 hours. Exhaust
gas temperature at rated output should not exceed 580°C (1,076°F). Top
piston to cylinder head clearance should be measured at 0.71 mm to 0.89
mm (0.028 in to 0.035 in).
Cylinder head bolts receive a torque of 83 Nm (61 lb-ft), equivalent to
8.5 kgm. A crosswise tightening sequence from the center outward must be
followed. Connecting rod cap nuts are torqued to 54 Nm (40 lb-ft),
equivalent to 5.5 kgm. Main bearing cap bolts receive a torque of 113 Nm
(83 lb-ft), equivalent to 11.5 kgm. The crankshaft V-pulley bolt is
torqued to 123 Nm (90 lb-ft), equivalent to 12.5 kgm. The flywheel bolts
are torqued to 78 Nm (58 lb-ft), equivalent to 8.0 kgm.
The damper disk bolts receive 25 Nm (18 lb-ft), equivalent to 2.6 kgm.
The rocker arm shaft bracket nuts are secured to 25 Nm (18 lb-ft).
Intake manifold bolts receive 20 Nm (15 lb-ft). Exhaust manifold nuts
are torqued to 25 Nm (18 lb-ft). The injection pump mounting nuts
receive 20 Nm (15 lb-ft). The injector hold-down nuts are torqued to 25
Nm (18 lb-ft).
The oil filter canister requires tightening to 15 Nm (11 lb-ft) or
three-quarters of a turn after gasket contact. The oil drain plug is
torqued to 40 Nm (30 lb-ft). The water pump mounting bolts receive 15 Nm
(11 lb-ft). The glow plugs are torqued to 15 Nm (11 lb-ft). The starter
motor mounting bolts are torqued to 35 Nm (26 lb-ft). The alternator
mounting bolts receive 25 Nm (18 lb-ft).
The Yanmar 3JH2E engine powers a range of marine vessels requiring
auxiliary or primary propulsion. Primary applications include sailboats
from 9 meters (30 ft) to 12 meters (40 ft) in length, where the engine
serves as auxiliary power for maneuvering in harbors and motoring during
calm conditions.
The engine is also found in small displacement fishing vessels including
trawlers and gillnetters. Workboat applications include small pilot
boats, harbor launches, and utility craft. The 3JH2E is often installed
as a replacement engine in older vessels due to its compact dimensions
and reliable service record.
The engine is distinct from the turbocharged Yanmar 3JH2TE (29 kW / 39
hp) and the larger Yanmar 3JH4E (36.8 kW / 50 hp) within the same JH
series family. A saildrive variant designated 3JH2CE exists, utilizing
an SD31 saildrive unit with counterclockwise propeller rotation when
viewed from the stern. A version with a 7-degree downward angle
transmission is designated 3JH2BE.
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