Yanmar 4JH45 Specifications
| Engine Model: Yanmar 4JH45 |
| Engine Type: 4-stroke inline 4-cylinder naturally aspirated water-cooled diesel |
| Total Displacement: 134 cu.in (2.19 L) |
| Rated Engine Power: 45 Hp (33.1 kW) at 3000 rpm |
| Fuel System Type: Common rail direct injection |
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The Yanmar 4JH45 is a four-cylinder, naturally
aspirated marine diesel engine from the JH-CR series. Engineered as a
replacement for the 4JH-ATE series, this engine represents a significant
advancement as the first small marine diesel to meet strict EPA Tier 3
emissions standards without requiring a turbocharger. Yanmar achieved
this compliance through the adoption of a common rail direct injection
system, which precisely controls fuel delivery across all engine speeds
and loads.
The Yanmar 4JH45 produces 45 hp (33.1 kW) at 3000 rpm for maximum
output, with a continuous rating of 40.9 hp (30.1 kW) at 2907 rpm. The
engine features a vertical, four-cycle, water-cooled design with
indirect freshwater cooling through a heat exchanger. A trochoid-type
lubrication pump supplies forced lubrication, assisted by an oil cooler
for temperature management.
The electronic control system includes an Engine Control Unit (ECU) with
CAN-bus and NMEA 2000 compatibility, enabling full integration with
modern vessel navigation and monitoring systems. The starting system
uses a 12V electric starter motor rated at 1.4 kW, paired with a
high-output 12V/125A alternator for demanding electrical loads. The
4JH45 is designed for displacement hull sailboats and power vessels in
the 35 to 45 foot range.
The Yanmar 4JH45 is a vertical, four-cycle, water-cooled diesel engine.
Total displacement measures 2.190 liters, equivalent to 134 cubic
inches. Bore is 88 mm (3.46 in) with a stroke of 90 mm (3.54 in),
producing a nearly square configuration. The combustion system uses
direct injection via a common rail fuel system. Aspiration is naturally
aspirated without turbocharging or aftercooling. Maximum output at the
crankshaft is 45 hp (33.1 kW) achieved at 3000 rpm. Continuous rating
output is 40.9 hp (30.1 kW) at 2907 rpm.
Maximum torque is 14.5 kg-m, equivalent to 142 Nm (105 lb-ft), delivered
across an engine speed range from 1800 to 2000 rpm. Idle speed is set to
750 rpm. Direction of rotation is counter-clockwise when viewed from the
flywheel end. Dry weight without gearbox is 220 kg (485 lb). The
electrical system operates at 12V DC. Cold valve clearance for both
intake and exhaust valves is 0.2 mm (0.008 in). Fuel must conform to EN
590 or ASTM D975 standards. Engine oil capacity including the filter is
5.8 liters (6.1 U.S. quarts). Coolant capacity is 5.8 liters (6.1 U.S.
quarts).
The cylinder block is constructed from high-strength cast iron with an
inline four-cylinder arrangement. The block is cast as a single piece
with integral cylinder bores, meaning no replaceable cylinder liners are
used. The bores are precision-machined directly into the parent cast
iron material and finished with a plateau-honed surface finish for
optimal ring sealing and oil retention. This parent bore design reduces
manufacturing complexity and eliminates liner sealing issues.
The cylinder block incorporates five main bearing webs with reinforced
bulkheads to support the crankshaft under continuous marine duty cycles.
A deep-skirt design extends the block below the crankshaft centerline,
providing enhanced torsional stiffness and vibration damping. The block
deck surface is machined flat to accept the cylinder head gasket.
Mounting pads are cast into the block for the common rail injection
pump, starter motor, alternator, and water pump.
An oil pan rail is machined on the lower face of the block. The block
includes a side-mounted spin-on oil filter housing and a dipstick tube
port. An integral timing gear housing is cast into the front face of the
block, housing the gear train that drives the camshaft, injection pump,
and water pump. A freshwater cooling jacket surrounds each cylinder bore
for the full stroke length.
A single cast-iron cylinder head spans all four cylinders. The head
incorporates a cross-flow design with intake ports on one side and
exhaust ports on the opposite side to optimize airflow. The valvetrain
operates as an overhead valve (OHV) configuration with two valves per
cylinder - one intake and one exhaust - for a total of eight valves. A
camshaft located within the cylinder block actuates the valvetrain.
Pushrods transfer motion through vertical bores in the cylinder head to
rocker arms mounted on a steel shaft. Hardened valve seat inserts are
pressed into the cylinder head, with exhaust seats manufactured from a
nickel-chromium heat-resistant alloy. Valve guides are pressed-in
cast-iron sleeves. Valve lash is adjustable using a screw-and-locknut
mechanism on each rocker arm, with a cold clearance of 0.2 mm (0.008 in)
set for both intake and exhaust valves.
The common rail direct injection system places the fuel injector
centrally in each cylinder head, oriented vertically to spray directly
into a shallow re-entrant bowl machined into the piston crown. The
cylinder head gasket is a multilayer steel (MLS) design with etched
sealing beads around each cylinder bore, oil galleries, and coolant
passages. Eight head bolts provide clamping force, with a
torque-to-yield procedure specified for final tightening.
The fuel system uses a common rail direct injection system, a first for
Yanmar in this power class. A gear-type fuel feed pump draws fuel from
the tank through a primary spin-on filter and water separator. The feed
pump supplies low-pressure fuel to the high-pressure supply pump. The
high-pressure supply pump, driven by the engine timing gears,
pressurizes fuel to extremely high levels and delivers it to the common
rail.
The common rail is a precision-machined accumulator tube that stores
pressurized fuel and maintains constant pressure regardless of engine
speed or load. An electronic high-pressure pump maintains rail pressure.
The Engine Control Unit (ECU) controls the pressure regulator valve on
the rail. Four electronically actuated injectors, one per cylinder,
connect to the common rail via short high-pressure lines.
Each injector contains a fast-switching solenoid that opens and closes
the nozzle at precise intervals commanded by the ECU. Injection timing,
duration, and pressure are fully variable under electronic control,
enabling multiple injection events per combustion cycle. A fuel return
line routes excess fuel and injector leakage back to the fuel tank. The
ECU monitors engine speed, coolant temperature, intake air temperature,
and rail pressure to calculate optimal injection parameters. A manual
fuel priming pump is provided for bleeding air after filter changes.
The lubrication system is a forced-feed design using a trochoid-type oil
pump. The trochoid pump consists of an inner rotor mounted on the
camshaft and an outer rotor, providing a compact, high-volume design
with few moving parts. Oil is drawn from the oil pan through a pick-up
tube fitted with a coarse mesh strainer. Total oil capacity including
the filter is 5.8 liters (6.1 U.S. quarts).
A spin-on full-flow oil filter is mounted on the side of the cylinder
block. The filter incorporates an integral bypass valve that opens when
the filter element becomes restricted. An oil cooler is integrated into
the lubrication circuit. The oil cooler is a seawater-cooled heat
exchanger, with seawater from the cooling system passing around a tube
bundle that carries engine oil. A pressure relief valve limits maximum
oil pressure.
The system supplies lubricant to the five main bearings, four connecting
rod bearings, camshaft bearings, rocker arm assembly, timing gears, and
the high-pressure fuel supply pump. Piston cooling jets direct oil
streams to the underside of each piston crown for thermal management.
The oil pan is constructed from stamped steel and includes a drain plug
with a magnetic insert. Recommended oil grade is SAE 15W-40 for most
marine operating conditions.
The cooling system uses indirect freshwater cooling with a heat
exchanger. A closed freshwater circuit containing antifreeze and
corrosion inhibitor circulates through the engine block, cylinder head,
and the oil cooler. A centrifugal freshwater pump is belt-driven from
the crankshaft pulley. A wax-pellet thermostat located in a housing on
the front of the cylinder head controls freshwater flow.
The thermostat begins to open at approximately 82°C (180°F) and reaches
full open at approximately 95°C (203°F). Freshwater passes through a
shell-and-tube heat exchanger mounted on the engine. Seawater is drawn
through a hull strainer by a flexible impeller-type raw water pump
mounted on the front of the engine. This seawater flows through the heat
exchanger, absorbing heat from the freshwater circuit before discharging
through the exhaust elbow to cool the exhaust gases.
A separate seawater path also passes through the oil cooler. The raw
water pump contains a neoprene impeller that requires periodic
inspection and replacement. A sacrificial zinc anode is installed in the
heat exchanger to prevent galvanic corrosion. Coolant capacity for the
freshwater circuit is 5.8 liters (6.1 U.S. quarts).
| Intake and Exhaust Systems |
Air Intake System: Ambient air passes through a dry-type air cleaner
mounted on the intake manifold. The intake manifold distributes air
evenly to each cylinder head intake port. No turbocharger or aftercooler
is present.
Exhaust System: A cast-iron exhaust manifold collects gases from all
four cylinders. The manifold connects to a water-cooled exhaust elbow.
Seawater from the cooling system injects into this elbow, mixing with
exhaust gases to cool them before they exit through the vessel's exhaust
hose.
The electrical system operates at 12V DC. A gear-reduction starter motor
rated at 1.4 kW is mounted on the flywheel housing. A high-output
belt-driven alternator produces 125 amps of charging current, sufficient
for heavy electrical loads including bow thrusters, windlasses, and
refrigeration systems.
Glow plugs are installed in the cylinder head, one per cylinder, as a
cold start aid. The ECU controls glow plug duration based on coolant
temperature. The system includes a warning buzzer and indicator lamps
for low oil pressure, high coolant temperature, and alternator failure.
Electronic Control System: The Engine Control Unit (ECU) manages all
engine functions including fuel injection timing, injection pressure,
idle speed, and cold start glow plug operation. The ECU accepts inputs
from sensors monitoring crankshaft position, camshaft position, coolant
temperature, intake air temperature, fuel rail pressure, and atmospheric
pressure. The ECU communicates via CAN-bus protocol and is NMEA 2000
compatible, allowing integration with vessel multifunction displays,
engine gauges, and alarm systems. A dedicated engine control panel
provides start/stop functions, tachometer, and diagnostic displays.
Engine Governor: Electronic governing is integrated into the ECU. The
ECU maintains engine speed under varying loads using feedback from the
crankshaft position sensor. The governor provides precise idle control,
rapid load acceptance, and stable speed holding.
Engine length measured from the front cover to the flywheel housing
mounting face is 800 mm (31.5 in). Width measured across the widest
points, including the common rail, injection pump, and exhaust manifold,
is 570 mm (22.4 in). Height measured from the oil pan rail to the top of
the rocker arm cover is 670 mm (26.4 in).
Dry weight of the complete engine, including the flywheel, common rail
system, heat exchanger, alternator, and starter motor, but excluding
oil, coolant, and transmission, is 220 kg (485 lb). The weight with a
full oil charge and coolant adds 15 kg (33 lb). When paired with a
Yanmar KMH series or other marine gearbox, add 35 to 50 kg (77 to 110
lb) depending on the transmission model. The shipping weight on a pallet
with protective packaging is 260 kg (573 lb).
Engine Oil: Capacity with filter: 5.8 l (6.1 U.S. qt). Oil change
interval: 250 hours or annually. Recommended grade: SAE 15W-40 or SAE
10W-30 meeting API CI-4 or higher. Oil Filter: Spin-on full-flow type.
Replace at every oil change. Coolant (Freshwater): Capacity: 5.8 l (6.1
U.S. qt). Change interval: 1000 hours or 2 years. Antifreeze
concentration: 40 to 50 percent with ethylene glycol. High Idle Speed
(No Load): 3150 rpm maximum.
Raw Water Pump Impeller: Flexible neoprene. Inspect at 250 hours.
Replace at 500 hours or annually. Fuel Filter (Primary): Spin-on with
water separator. Replacement interval: 250 hours. Fuel Filter
(Secondary): Spin-on on the engine. Replacement interval: 500 hours.
Valve Lash (Cold): Intake: 0.20 mm (0.008 in). Exhaust: 0.20 mm (0.008
in). Inspection interval: 500 hours. Air Cleaner: Dry paper element.
Clean at 250 hours. Replace at 500 hours. Low Idle Speed: 750 rpm.
Injector Service: Inspect and test flow rate every 1000 hours. Replace
nozzle tips as required. Glow Plugs: Resistance check at 500 hours.
Replace if open circuit. Engine Mounts: Inspect for cracking and sagging
at 500 hours. Heat Exchanger Zinc Anode: Inspect at 250 hours. Replace
when reduced to 50 percent of original size. ECU Diagnostic Scan:
Perform at 1000 hours to check for fault codes. Thermostat: Begins
opening at 82°C (180°F). Fully open at 95°C (203°F).
Cylinder Head Bolts (M10 x 1.25): 25 Nm (18 lb-ft).
Connecting Rod Cap Nuts (M9 x 1.0): 35 Nm (26 lb-ft).
Main Bearing Cap Bolts (M10 x 1.25): 50 Nm (37 lb-ft).
Flywheel Bolts (M10 x 1.25): 50 Nm (37 lb-ft).
Crankshaft Pulley Bolt (M14 x 1.5): 120 Nm (89 lb-ft).
Camshaft Thrust Plate Bolts (M6 x 1.0): 12 Nm (9 lb-ft).
Rocker Arm Shaft Support Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
Rocker Arm Adjustment Lock Nut (M6 x 1.0): 10 Nm (7 lb-ft).
Valve Cover Nuts (M6 x 1.0): 8 Nm (6 lb-ft).
Common Rail Mounting Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
High Pressure Supply Pump Mounting Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
Injector Hold-Down Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
Glow Plugs (M10 x 1.0): 15 Nm (11 lb-ft).
Oil Pan Drain Plug (M12 x 1.5): 35 Nm (26 lb-ft).
Starter Motor Mounting Bolts (M10 x 1.25): 40 Nm (30 lb-ft).
Alternator Pivot Bolt (M8 x 1.25): 25 Nm (18 lb-ft).
Raw Water Pump Mounting Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Freshwater Pump Mounting Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Thermostat Housing Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Exhaust Manifold Nuts (M8 x 1.25): 25 Nm (18 lb-ft).
Intake Manifold Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Engine Mount Bracket Bolts (M10 x 1.25): 45 Nm (33 lb-ft).
Heat Exchanger Mounting Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
The Yanmar 4JH45 engine serves exclusively in marine applications as a
propulsion unit. Sailboats (Auxiliary Power): Mid-sized sailboats from
38 to 45 feet length overall (LOA). Common installations include
Beneteau Oceanis 38, 40, 41, and 43 models. Jeanneau Sun Odyssey 389,
419, and 439. Hunter 39, 40, and 41 sailboats. Catalina 385, 387, and
425. Dufour 382, 412, and 430. Bavaria Cruiser 39, 40, and 42. Hanse
388, 408, and 418.
Powerboats (Displacement and Semi-Displacement Vessels): Trawler yachts
from 35 to 42 feet. Down-East style cruisers. Pocket trawlers requiring
reliable, fuel-efficient propulsion. Commercial Vessels: Small fishing
boats and gillnetters. Aquaculture workboats and supply vessels. Pilot
boats and harbor security craft. Transmission Options: Yanmar KMH series
marine gearboxes with hydraulic clutch.
Reduction ratios ranging from 2.2:1 to 3.1:1 forward rotation. Saildrive
option with SD series lower unit for direct hull mounting without a
traditional shaft. Generator Applications: The 4JH45 is also used as a
marine generator prime mover (designated 4JH45-MG) in the 9-12 kW
continuous power range, running at 1500 rpm for 50 Hz or 1800 rpm for 60
Hz systems on larger yachts and small commercial vessels.
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