Yanmar 4JH3 DTE Specifications
| Engine Model: Yanmar 4JH3 DTE |
| Engine Type: 4-stroke inline 4-cylinder turbocharged water-cooled diesel |
| Total Displacement: 121.7 cu.in (1.99 L) |
| Rated Engine Power: 125 Hp (91.9 kW) at 3800 rpm |
| Fuel System Type: Direct injection |
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The Yanmar 4JH3-DTE is a 4-cylinder,
turbocharged and intercooled marine diesel engine belonging to the JH3
series. This series introduced direct injection for improved fuel
efficiency and lower emissions compared to the preceding JH2 series.
Designed for displacement and planing hulls, this power unit serves both
pleasure and light commercial marine applications including sailboats,
sport cruisers, and small fishing vessels. The engine incorporates a
fresh water cooling system with a heat exchanger, a standard
configuration for marine propulsion where seawater is used to reject
engine heat to the environment.
The direct injection combustion system provides better fuel atomization
and reduced specific fuel consumption compared to indirect injection
designs of similar displacement. A 12-volt electric starting system with
a high-output alternator supports onboard electrical demands. The engine
is available with multiple transmission options including the KM4A1,
KBW21, and KMH4A hydraulic gearboxes, as well as the SD50 sail drive for
sailboat applications. The 4JH3-DTE meets EPA Tier 2 and RCD emissions
standards.
The Yanmar 4JH3-DTE is an inline, four-cylinder, four-cycle,
water-cooled diesel engine. Its architecture employs a direct injection
combustion system with a Bosch VE-type distributor injection pump. The
aspiration system uses a turbocharger combined with a seawater-cooled
intercooler that reduces intake air temperature after compression,
increasing charge density and reducing thermal load on pistons and
valves. The cylinder block features replaceable dry-type cylinder
liners. The engine rotates counterclockwise when viewed from the
flywheel side.
Engine Type: Inline 4-cylinder, 4-cycle, water-cooled diesel
Engine Family: Yanmar JH3 Series
Displacement: 1.995 L (121.7 cu.in)
Bore x Stroke: 84 mm x 90 mm (3.31 in x 3.54 in)
Compression Ratio: 18.0:1
Combustion System: Direct Injection (DI)
Aspiration: Turbocharged with Intercooler
Maximum Output (Crankshaft): 91.9 kW (125 hp) @ 3800 rpm
Continuous Rating: 81 kW (110 hp) @ 3700 rpm
Maximum Torque: 280 Nm (206 lb-ft) @ 2400-2600 rpm
Cruising RPM Range: 3200-3400 rpm
Firing Order: 1-3-4-2
Direction of Rotation: Counterclockwise viewed from flywheel
Emissions Standards: EPA Tier 2, RCD, BSO II, EMC
The cylinder block is a single-piece, inline construction manufactured
from high-grade cast iron. This material provides the rigidity required
to withstand combustion pressures generated by the turbocharged direct
injection system. The block is of an open-deck design with the cylinder
bores supported along their full length. Replaceable dry-type cylinder
liners are pressed into the block, allowing for overhaul without
replacing the entire crankcase.
Each liner is centrifugally cast from alloyed iron and finished with a
plateau honing process that promotes oil retention and rapid piston ring
seating. The crankcase forms a deep-skirt design extending below the
crankshaft centerline, with the oil pan mounting flange cast integrally
into the block.
Five main bearing bulkheads support the crankshaft, with each bearing
cap secured by two vertical bolts. The water jacket surrounds all four
cylinders completely, fed by the fresh water pump through cast-in
passages. The block incorporates an integral oil gallery that
distributes pressurized lubricant to all main bearings and to the piston
cooling jets.
The cylinder head is manufactured from cast iron, matching the block
material for uniform thermal expansion and preventing head gasket
failure. The cross-flow design positions intake ports on one side and
exhaust ports on the opposite side, minimizing heat transfer from the
exhaust manifold to the incoming air charge.
Each cylinder features four valves arranged symmetrically: two intake
valves and two exhaust valves, for a total of sixteen valves across all
four cylinders. Valves are made from heat-resistant steel with
induction-hardened tips. Valve seats are pressed-in inserts made from
sintered alloy material. Valve actuation occurs via a single overhead
camshaft using roller rocker arms with adjustable pushrods.
Valve clearance adjustment is performed using setscrews and locknuts at
the rocker arm tips. The centrally located fuel injector passes through
the cylinder head between the four valves, directing the fuel spray
directly into the combustion chamber recess in the piston crown. Glow
plugs are installed in each cylinder as a cold starting aid.
The fuel system is a direct injection architecture with a Bosch VE-type
distributor injection pump. A self-priming diaphragm-type fuel lift pump
draws fuel from the tank and delivers it through a replaceable
cartridge-type fuel filter with an integral water separator. The
injection pump is mounted on the engine and driven by the gear train.
This pump contains a single plunger that distributes fuel sequentially
to each of the four cylinders through a rotating distributor head. A
mechanical centrifugal governor integrated into the injection pump
maintains engine speed under varying load by adjusting fuel delivery
volume.
A pneumatic or mechanical boost compensator adjusts fuel delivery based
on turbocharger boost pressure. High-pressure injection lines,
manufactured from seamless steel tube, carry fuel from the pump to the
four injection nozzles. Each nozzle is a multi-hole injector with an
opening pressure of 200-210 bar. Excess fuel from the injection pump and
injectors returns to the tank through a spill line. A manual priming
lever on the lift pump allows system priming after filter changes.
The lubrication system is a forced-feed, wet-sump configuration with a
full-flow filtration circuit. A trochoid-type oil pump, mounted on the
engine front cover and driven by the crankshaft, draws oil from the sump
through a screened pick-up tube. A spring-loaded pressure relief valve
maintains system pressure within a calibrated range of 3-5 bar at rated
speed.
Oil passes through a full-flow spin-on cartridge filter containing a
paper filtration element with a bypass valve that opens when filter
restriction exceeds 1.5-2.0 bar. Pressurized oil is distributed through
internal galleries to the five main bearings, four connecting rod
bearings via drilled crankshaft passages, camshaft bearings, rocker arm
shaft, turbocharger bearing cartridge, and injection pump drive.
Piston cooling jets direct oil to the underside of each piston crown. A
plate-type oil cooler, integrated into the engine block and using engine
fresh water as the exchange medium, maintains oil temperature within
operational limits. An oil dipstick passes through the cylinder block
into the sump for level checks. The oil pan is a fabricated steel or
cast aluminum component with a drain plug at its lowest point.
The cooling system is a dual-circuit design: a pressurized fresh water
circuit for engine cooling and a separate seawater circuit for heat
rejection. The fresh water circuit is thermostatically controlled. A
belt-driven, centrifugal fresh water pump circulates coolant through the
cylinder block, cylinder head, turbocharger center housing, oil cooler,
and the heat exchanger.
A wax-pellet thermostat begins opening at 71-76°C and reaches full open
at 85-90°C, providing a coolant bypass circuit during engine warm-up.
The heat exchanger is a shell-and-tube type where fresh water flows
inside tubes while seawater passes over the tube bundle. The seawater
circuit uses a rubber-impeller, positive-displacement pump driven by the
front belt system.
Seawater is drawn through a strainer, then passes through the heat
exchanger, the charge air cooler (intercooler), and the water-injected
exhaust elbow before discharge overboard. An expansion tank accommodates
thermal expansion and provides de-aeration. A radiator-type pressure cap
maintains the fresh water circuit at 0.5-1.0 bar above atmospheric
pressure.
| Intake and Exhaust Systems |
Intake System: Air enters through a flame arrestor, passes through the
turbocharger compressor housing, then through the seawater-cooled charge
air cooler (intercooler), and finally into the intake manifold. The
intake manifold distributes air equally to all four cylinders. An intake
air heater is not fitted, as glow plugs provide cold start assistance.
Exhaust System: The exhaust manifold is water-cooled, cast from
corrosion-resistant material. Exhaust gases exit the cylinder head,
drive the turbocharger turbine wheel, then pass through the water-cooled
exhaust elbow where seawater is injected to cool gases before entering
the exhaust hose and overboard discharge.
Starting System: A 12-volt electric starting system is standard, with a
1.4 kW or 1.8 kW starter motor. A solenoid-shift mechanism engages the
pinion gear with the ring gear mounted on the flywheel before supplying
full cranking current. Glow plugs provide cold starting assistance,
energizing for 5-10 seconds before cranking.
Charging System: A 12-volt alternator charges the battery and powers
vessel electrical loads. Standard alternator output is 80A, with a 60A
or 125A option available depending on application. The alternator is
driven by a poly-V belt with an automatic tensioner.
Length (with KM4A2 gearbox): 1001 mm (39.4 in)
Length (without gearbox): 914 mm (36.0 in)
Width: 581 mm (22.9 in)
Height: 661 mm (26.0 in)
Dry Weight (without transmission): 229 kg (505 lb)
0Oil and Oil Filter Change: Every 250 hours or 12 months
Initial Oil Change (first 50 hours): Required
Fuel Filter Replacement: Every 250 hours
Fuel Filter Water Separator Drain: Weekly or every 50 hours
Seawater Pump Impeller Inspection: Every 200 hours
Seawater Pump Impeller Replacement: Every 500 hours or 12 months
Drive Belt Inspection: Every 250 hours
Drive Belt Replacement: Every 500 hours
Valve Clearance Inspection: Every 500 hours
Coolant Level Check: Daily before starting
Coolant Replacement: Every 1000 hours or 24 months
Heat Exchanger Anode Inspection: Every 250 hours
Engine Oil Capacity (with filter): 7.0 L (7.4 US qt)
Recommended Oil Grade: SAE 15W-40 (API CI-4 or higher)
Fresh Water Capacity (engine + heat exchanger): 7.2 L (7.6 US qt)
Seawater Circuit Capacity: Dependent on vessel plumbing
Recommended Coolant: Ethylene glycol-based antifreeze
Valve Clearance (intake and exhaust, cold engine): 0.20 mm (0.008 in)
Cylinder Head Bolts (M12): 90 ± 10 Nm (66 ± 7 lb-ft)
Main Bearing Cap Bolts (M12): 90 ± 10 Nm (66 ± 7 lb-ft)
Connecting Rod Cap Bolts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
Flywheel Bolts (M12): 90 ± 10 Nm (66 ± 7 lb-ft)
Camshaft Bearing Cap Bolts (M8): 26 ± 3 Nm (19 ± 2 lb-ft)
Rocker Arm Shaft Support Bolts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
Rocker Arm Adjusting Locknuts (M6): 11 ± 1 Nm (8 ± 1 lb-ft)
Injector Clamp Bolts (M8): 26 ± 3 Nm (19 ± 2 lb-ft)
High-Pressure Injection Line Nuts (M12 x 1.5): 25-30 Nm (18-22 lb-ft)
Glow Plugs (M8): 15-20 Nm (11-15 lb-ft)
Oil Filter (spin-on): 18-22 Nm (13-16 lb-ft)
Oil Pan Bolts (M8): 26 ± 3 Nm (19 ± 2 lb-ft)
Water Pump Mounting Bolts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
Thermostat Housing Bolts (M8): 26 ± 3 Nm (19 ± 2 lb-ft)
Intake Manifold Nuts (M8): 26 ± 3 Nm (19 ± 2 lb-ft)
Exhaust Manifold Nuts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
Turbocharger Mounting Nuts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
Starter Motor Mounting Bolts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
Alternator Pivot and Adjusting Bolts (M10): 50 ± 5 Nm (37 ± 4 lb-ft)
The Yanmar 4JH3-DTE engine is designed exclusively for marine propulsion
in recreational and light commercial vessels.
Pleasure Boats: Sport cruisers, express cruisers, flybridge motor
yachts, and cabin cruisers requiring 100-125 horsepower. Commonly
installed in boats of 8-12 meters in length.
Sailboats: Large displacement auxiliary sailboats using the SD50 sail
drive configuration. Provides reliable auxiliary power for cruising
yachts of 11-14 meters.
Light Commercial Vessels: Patrol boats, pilot boats, water taxis, small
fishing vessels, and dive boats requiring dependable propulsion with low
fuel consumption.
Powerboats: Planing hulls including center console, cuddy cabin, and
walkaround vessels operating in coastal and offshore environments.
Transmission Options: KM4A1 mechanical gearbox, KBW21 mechanical
gearbox, KMH4A hydraulic gearbox, and SD50 sail drive for sailboat
installations.
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