Yanmar 4LH DTE Specifications
| Engine Model: Yanmar 4LH DTE |
| Engine Type: 4-stroke inline 4-cylinder turbocharged water-cooled diesel |
| Total Displacement: 210.9 cu.in (3.45 L) |
| Rated Engine Power: 170 Hp (125 kW) at 3300 rpm |
| Fuel System Type: Direct injection |
____________________________________________________________________________________
The Yanmar 4LH-DTE is a 4-stroke, vertical,
water-cooled marine diesel engine featuring direct injection,
turbocharging, and an intercooler. This inline-4 cylinder powerplant
belongs to Yanmar's LH series, which is engineered for high performance
in commercial and recreational marine applications. The "DTE"
designation denotes a turbocharged and aftercooled configuration with
direct injection.
The engine is widely recognized for its robust construction, compact
design, and excellent power-to-weight ratio, making it a preferred
choice for fishing vessels, patrol boats, yachts, and workboats. Its
combination of electronic management and mechanical durability meets
demanding operational requirements while providing fuel efficiency and
compliance with marine emission standards.
The Yanmar 4LH-DTE occupies a prominent position as a mid-range marine
diesel, balancing significant power output with a compact physical
footprint. The engine displaces 3.455 liters, achieved through bore and
stroke dimensions of 100 mm by 110 mm. This square geometry supports
strong torque delivery across a wide engine speed range. The compression
ratio is 16.5:1, enabling efficient cold starting and complete
combustion.
The direct injection fuel system is complemented by a turbocharger and
intercooler (aftercooler), which increases intake air density for more
efficient combustion, resulting in higher power output from the
displacement. Maximum output is 170 horsepower (125 kW) at 3,300 rpm,
with a maximum torque of 700 Nm delivered at a low 1,400 rpm. The
valvetrain uses an overhead valve (OHV) arrangement with pushrods and
rocker arms. Its multi-cylinder design ensures smooth operation with
lower vibration levels compared to three-cylinder models. The forced
lubrication system employs a gear-type pump circulating oil through a
full-flow filter.
The dry weight of the engine is 406 kg (895 lb) without a marine gear,
facilitating installation in a variety of vessel types. The 12-volt
electrical system includes a 2.5 kW starter motor and a 55 ampere
alternator. The engine is commonly paired with the KM5A reversing
gearbox and uses SAE #4 or SAE #3 flywheel housings depending on the
application. When maintained correctly with regular service intervals,
this engine provides long-term reliability in harsh marine environments.
Engine Type: 4-stroke, vertical, water-cooled, inline-4 diesel
Valvetrain: Overhead Valve (OHV), 8 valves (2 per cylinder) with
pushrods
Aspiration: Turbocharged with intercooler (aftercooler)
Displacement: 3.455 L (210.9 cu.in)
Bore: 100.0 mm (3.94 in)
Stroke: 110.0 mm (4.33 in)
Compression Ratio: 16.5:1
Combustion System: Direct injection
Maximum Output (Marine): 170 hp (125 kW) @ 3,300 rpm
Maximum Torque: 700 Nm (516 lb-ft) @ 1,400 rpm
Maximum Engine Speed (Rated): 3,300 rpm
Low Idle Speed: 650-750 rpm (factory adjustable)
Direction of Rotation (viewed from stern): Counterclockwise
The cylinder block is a monobloc casting manufactured from high-strength
gray cast iron with additional alloying elements for corrosion
resistance in saltwater environments. The block incorporates replaceable
cylinder liners, which are either wet-type or dry-type depending on the
specific production variant. The liners are designed to resist wear and
corrosion under sustained high-load operation. The block uses an
open-deck configuration with integral water jackets surrounding each
cylinder.
Five main bearing bulkheads are cast integrally with the block,
supporting a forged steel crankshaft with induction-hardened journal
surfaces. The crankcase extends below the crankshaft centerline, forming
a rigid structure that minimizes vibration under load. Engine mounting
feet are cast into the block sides for flexible mounts that isolate
vibration from the hull. The timing gear housing at the front of the
block contains the gear train driving the camshaft and injection pump.
The cylinder head is a single, cross-flow casting manufactured from cast
iron. The combustion chambers are of the direct-injection open type,
machined into the piston crown. The cylinder head carries two valves per
cylinder: one intake and one exhaust, arranged in a straight line along
the head centerline. Valves are constructed from heat-resistant
silichrome steel, with exhaust valves featuring hardened seats for
durability under high exhaust gas temperatures generated by
turbocharging.
The valvetrain operates via a camshaft located in the cylinder block.
Mechanical lifters (solid tappets) follow the camshaft lobes and
transfer motion through hardened pushrods to rocker arms. The rocker
arms pivot on a through-shaft mounted above the cylinder head. Valve
lash adjustment uses a screw-and-locknut arrangement at the rocker
arm-to-valve stem interface. Adjustments are performed with the engine
cold. The cylinder head gasket is a multi-layer steel (MLS) design with
elastomer sealing beads.
The fuel system is a mechanical direct-injection design. An in-line
injection pump, commonly a Bosch-type or Yanmar-manufactured unit, is
mounted on the cylinder block and driven by the timing gear train. The
pump contains four individual pumping plungers, one per cylinder. The
pump includes a mechanical centrifugal governor that maintains engine
speed under varying loads by adjusting fuel delivery. A mechanical
diaphragm-type feed pump, mounted on the injection pump body, draws fuel
from the tank and delivers it through a water-separating fuel filter to
the injection pump.
The system is equipped with advanced fuel injection technology to
optimize consumption and enhance long-term cost savings. Each cylinder
has a multi-hole injector nozzle mounted vertically in the cylinder
head. Injectors are spring-loaded, calibrated to open at a precise
pressure. Excess fuel not injected returns to the fuel tank through a
return line for pump cooling. The injection pump timing is set using a
dial indicator and shims.
The lubrication system is a forced, full-flow wet-sump design. A
gear-type oil pump is mounted internally on the front of the crankshaft
within the timing gear case. The pump draws oil through a screened
pickup tube from a cast aluminum oil pan. The total system oil capacity
(including the full-flow spin-on oil filter) is 11.5 liters (12.2 qt).
Oil passes through the pump and then through the full-flow spin-on oil
filter mounted on the cylinder block.
An integral bypass valve within the filter housing allows unfiltered oil
to circulate if the filter becomes restricted. From the filter,
pressurized oil enters the main oil gallery, a longitudinal passage
drilled through the cylinder block. The main gallery distributes oil to
all five main bearings through cross-drilled passages. Connecting rod
bearings receive oil from the main bearings via diagonal passages
drilled through the crankshaft.
A separate vertical passage in the cylinder block carries oil to the
cylinder head. Oil pressure is regulated by a spring-loaded relief valve
located on the oil pump housing. A turbocharger oil feed line, supplied
from the main gallery, routes pressurized oil to the turbocharger center
housing. The recommended oil grade is SAE 15W-40, diesel-rated (API
CF-4, CG-4, CH-4, or higher).
The cooling system is an indirect freshwater (closed) cooling design
with a separate seawater circuit. The freshwater circuit is sealed and
thermostatically controlled. A belt-driven centrifugal fresh water pump
circulates coolant through the cylinder block water jacket, cylinder
head, and the tube side of a tubular heat exchanger. A wax-pellet
thermostat is located in a housing at the front of the cylinder head.
The thermostat is rated to begin opening at 71-76°C (160-169°F) and is
fully open by 85°C (185°F). When the thermostat is closed, coolant
recirculates within the engine for rapid warm-up. When open, coolant
flows through the heat exchanger. The seawater circuit uses a
rubber-impeller raw water pump, belt-driven from the crankshaft pulley.
The raw water pump draws seawater through a hull inlet and strainer and
then pumps it through the shell side of the heat exchanger, absorbing
heat from the freshwater coolant.
From the heat exchanger, seawater is injected into the exhaust mixing
elbow to cool exhaust gases before discharge overboard. The system
includes a coolant recovery reservoir connected to the heat exchanger
filler neck. The freshwater cooling capacity is 14.8 liters (15.6 qt). A
galvanic corrosion protection system (zinc anode) is installed in the
heat exchanger to prevent electrolytic damage.
| Intake and Exhaust Systems |
Intake System: Air enters through a flame-arresting intake silencer (air
cleaner) that reduces intake noise while preventing flame propagation
from the engine into the engine room in the event of a backfire. From
the silencer, air flows to the turbocharger compressor inlet. The
compressor discharges heated, compressed air into the intercooler
(aftercooler), which reduces intake air temperature before air enters
the intake manifold. The manifold distributes charge air evenly to all
four cylinders.
Exhaust System: A cast-iron exhaust manifold collects exhaust gases from
all four cylinders and routes them to the turbocharger turbine housing
inlet. The manifold is designed to expand thermally without cracking.
From the turbocharger outlet, exhaust flows through a water-cooled
mixing elbow. The mixing elbow injects seawater from the raw water pump
into the exhaust stream, cooling gases to below 100°C (212°F) before
discharge through a water-lift muffler and through-hull fitting.
The engine is equipped with a 12-volt, negative-ground marine electrical
system. A 12-volt, 2.5 kW starter motor engages the flywheel ring gear
through a solenoid. The charging system uses a 12-volt, 55 ampere
alternator, which provides sufficient capacity for multiple batteries
and onboard electronics.
Turbocharger System: The engine is equipped with a single,
fixed-geometry turbocharger, commonly a K26 series unit. The
turbocharger is mounted directly on the exhaust manifold. Exhaust gas
flow spins the turbine wheel, which drives the compressor wheel on the
same shaft. The compressor draws ambient air through the air cleaner and
compresses it, increasing air density and enabling more fuel to be
burned per cycle. The intercooler reduces the temperature of the
compressed air, further increasing its density and improving combustion
efficiency. The turbocharger center housing includes an oil feed and
return port for bearing lubrication.
Starting Aid: A cold start advance system integrated into the injection
pump advances injection timing during cranking when coolant temperature
is below a threshold (approximately 5°C / 41°F).
Air Compressor (for Air Brake Equipped Vessels): On vessels equipped
with pneumatic systems, an optional single-cylinder air compressor is
gear-driven from the engine timing gear train. The compressor mounts to
the side of the cylinder block or timing gear housing.
Overall Engine Length (Front Pulley to Flywheel Housing): 941-1,173 mm
(37.0-46.2 in)
Overall Engine Width: 673-1,051 mm (26.5-41.4 in)
Overall Engine Height (From Oil Pan Rail to Valve Cover Top): 768-1,020
mm (30.2-40.2 in)
Dry Weight (Engine Only, No Fluids, No Transmission): 406 kg (895 lb)
Weight (With Fluids and KM5A Marine Gear): 440-450 kg (970-992 lb)
Engine Oil:
Grade: SAE 15W-40 or SAE 10W-40 (diesel-rated, API CF-4, CG-4, CH-4, or
higher).
Capacity (Total System, With Filter): Approx. 11.5 L (12.2 qt).
Normal Pressure (Rated Speed, Hot): 350-450 kPa (51-65 psi).
Minimum Pressure (Hot Idle): 70 kPa (10 psi).
Engine Oil Change Interval: Change every 150-250 hours or annually.
Oil Filter Change Interval: Replace at every oil change.
Cooling System (Freshwater Circuit):
Coolant Type: Diesel-rated ethylene glycol antifreeze.
Total Freshwater Capacity (Engine and Heat Exchanger): 14.8 L (15.6 qt).
Thermostat Opening Temperature: 71-76°C (160-169°F).
Thermostat Full Open Temperature: 85°C (185°F).
Heat Exchanger Pressure Cap Rating: 0.7-1.0 bar (10-15 psi).
Coolant Change Interval: Drain, flush, and refill every 1,000 hours or
every 2 years.
Valve Clearance (Cold Engine):
Intake: 0.25-0.30 mm (0.010-0.012 in)
Exhaust: 0.30-0.35 mm (0.012-0.014 in)
Valve Adjustment Interval: Inspect and adjust every 500 operating hours
or annually.
Fuel Filter Change Interval (Pre-filter and Secondary): Replace every
250-300 operating hours or annually. Drain water from pre-filter
separator monthly. Timing Gear Train: Gear-driven camshaft requires no
periodic replacement. Impeller Replacement (Seawater Pump): Replace
rubber impeller every 250-500 hours or annually. Injector Testing
Interval: Test injector opening pressure and spray pattern every
1,000-2,000 operating hours. Recalibrate or replace as needed.
Turbocharger Inspection: Inspect shaft end-play and radial clearance
every 1,500 operating hours.
Cylinder Head Bolts, Step 1: 50 Nm (37 lb-ft).
Cylinder Head Bolts, Step 2: 100 Nm (74 lb-ft).
Cylinder Head Bolts, Step 3: 140 Nm (103 lb-ft).
Cylinder Head Bolts, Step 4 (final): 170 Nm (125 lb-ft).
Connecting Rod Cap Bolts: 65-70 Nm (48-52 lb-ft).
Main Bearing Cap Bolts: 120-130 Nm (89-96 lb-ft).
Flywheel Bolts (to Crankshaft Flange): 100-110 Nm (74-81 lb-ft).
Crankshaft Pulley Bolt (Front Damper): 250-300 Nm (184-221 lb-ft).
Camshaft Drive Gear Bolt: 80-90 Nm (59-66 lb-ft).
Injection Pump Mounting Nuts (to Timing Gear Housing): 30-35 Nm (22-26
lb-ft).
High-Pressure Injection Lines (Injector End, Pump End): 25-30 Nm (18-22
lb-ft).
Injector Hold-Down Clamp Bolts: 25-30 Nm (18-22 lb-ft).
Intake Manifold Bolts: 20-25 Nm (15-18 lb-ft).
Exhaust Manifold Nuts (to Cylinder Head): 35-40 Nm (26-30 lb-ft).
Turbocharger Mounting Nuts (to Exhaust Manifold): 45-50 Nm (33-37
lb-ft).
Turbocharger Oil Feed Line Fittings: 25-30 Nm (18-22 lb-ft).
Oil Pan Bolts (Cast Aluminum Pan): 15-18 Nm (11-13 lb-ft).
Valve Cover Bolts: 8-10 Nm (6-7 lb-ft).
Thermostat Housing Bolts: 15-20 Nm (11-15 lb-ft).
Fresh Water Pump Mounting Bolts: 20-25 Nm (15-18 lb-ft).
Seawater Raw Water Pump Mounting Bolts: 18-22 Nm (13-16 lb-ft).
Starter Motor Mounting Bolts: 35-40 Nm (26-30 lb-ft).
Alternator Mounting Bracket Bolts: 30-35 Nm (22-26 lb-ft).
Engine Flexible Mount Nuts (Engine to Mount Bracket): 45-55 Nm (33-41
lb-ft).
Oil Drain Plug (Oil Pan): 35-40 Nm (26-30 lb-ft).
The Yanmar 4LH-DTE engine is utilized as the primary marine propulsion
engine for the following vessel types.
Commercial Fishing Vessels:
Small coastal and offshore fishing boats.
Trawlers, longliners, and purse seiners.
Patrol and Security Vessels:
Coast guard patrol boats.
Maritime police and customs craft.
Workboats:
Small to mid-sized tugs and push boats.
Crew transfer vessels for offshore platforms and wind farms.
Harbor utility vessels and barges.
Recreational Vessels:
Motor yachts and express cruisers.
Sportfishing boats.
Charter and eco-tourism vessels.
Passenger Vessels:
Small passenger ferries (lake, river, and coastal routes).
Tour boats and water taxis.
____________________________________________________________________________________
| Industrial Engines Technical Specifications |
| Car Engines Technical Specifications |
| Small Engines Technical Specifications |
| Outboard Engines Technical Specifications |
