Yanmar 4LH STE Specifications
| Engine Model: Yanmar 4LH STE |
| Engine Type: 4-stroke inline 4-cylinder turbocharged water-cooled diesel |
| Total Displacement: 210.9 cu.in (3.45 L) |
| Rated Engine Power: 230 Hp (169.1 kW) at 3300 rpm |
| Fuel System Type: Direct injection |
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The Yanmar 4LH-STE is a high-output, 4-stroke,
vertical water-cooled marine diesel engine. It is the most powerful
variant in the 4LH series, featuring mechanical fuel injection and a
robust turbocharger/intercooler setup. This engine is designed for
planing powerboats, offshore cruisers, and light commercial vessels
requiring a compact, lightweight, high-power-density diesel powerplant.
The Yanmar 4LH-STE delivers 230 horsepower at 3,300 rpm while
maintaining the durability expected of a Yanmar marine engine. The
turbocharged and intercooled configuration provides strong torque across
a wide operating range. This engine is frequently paired with hydraulic
multi-disc clutch gearboxes such as the KMH50A and ZF63A. A thermostat
with an opening temperature of 71°C (160°F) regulates coolant flow. The
engine is approved for use with Hydrotreated Vegetable Oil (HVO) as a
drop-in fuel replacement for fossil diesel.
The Yanmar 4LH-STE is a four-stroke, water-cooled, turbocharged and
intercooled, inline 4-cylinder diesel engine. The cylinder arrangement
is vertical and in-line, designed for compact mounting in marine engine
compartments. The engine block is constructed from cast iron, while the
cylinder head is an aluminum alloy or cast iron unit depending on the
production year.
The valvetrain is an overhead valve (OHV) design with pushrods and
rocker arms, actuated by a camshaft located in the cylinder block. Each
cylinder features two valves - one intake and one exhaust. Maximum
output is 169.1 kW (230 hp) at 3,300 rpm. Continuous rating is 140 kW
(190 hp) at 3,100 rpm. Displacement is 3,455 cc (210.8 cu.in), achieved
through a bore of 100.0 mm (3.94 in) and a stroke of 110.0 mm (4.33 in).
The compression ratio is 16.5:1. Maximum torque is 630 Nm (465 lb-ft) at
2,400 to 2,600 rpm. Idle speed is approximately 700 rpm. Maximum
continuous rpm is 3,100 rpm, with a recommended long-term durability
cruise range of 2,900 to 3,000 rpm.
The combustion system is direct injection. Aspiration is provided by a
turbocharger with an intercooler (charge air cooler). The cooling system
is fresh water cooling (indirect) via a centrifugal circulation pump and
a rubber impeller seawater pump. The lubrication system is an enclosed,
forced lubricating system. The electrical system includes a 12V starting
motor (2.5 kW) with an 80A alternator. Engine rotation is
counter-clockwise when viewed from the stern (flywheel side). The firing
order for a 4-cylinder engine is 1-3-4-2.
The cylinder block is a cast iron, closed-deck design. This construction
provides high rigidity and excellent bore retention under the elevated
thermal and mechanical loads generated by turbocharged operation. The
water jacket surrounds each cylinder bore fully, promoting even cooling
across the engine. The block is configured for compact mounting in
marine engine compartments, with the engine mounts positioned at the
front and rear of the block.
The crankshaft is forged or cast nodular iron, supported by five main
bearings. The five-main-bearing configuration is standard for a
4-cylinder engine, providing adequate support for the firing impulses
under sustained high-load operation. Connecting rods are forged steel.
Pistons are aluminum alloy with two compression rings and one
oil-control ring. The piston skirts feature a coating to reduce friction
during cold starts. No cylinder liners are used; the bores are machined
directly into the cast iron. However, a zinc anode is installed in the
seawater cooling circuit to prevent galvanic corrosion.
The cylinder head is an aluminum alloy or cast iron cross-flow casting
with a direct injection combustion chamber design. The cross-flow
arrangement places the intake manifold on one side of the head and the
exhaust manifold on the opposite side, improving volumetric efficiency
and reducing heat transfer to the intake charge. The camshaft is located
in the cylinder block and actuates the valves through mechanical
lifters, pushrods, and rocker arms.
The valve train includes adjustable rocker arms with screw-type
adjusters and locking nuts, allowing precise valve clearance setting.
Intake and exhaust valves are fitted with hardened tip inserts to reduce
wear at the rocker arm contact point. Valve seats are induction-hardened
directly into the head or fitted with replaceable inserts. Valve guides
are also integral to the head casting or replaceable. The cylinder head
gasket is a multi-layer steel design capable of withstanding cylinder
pressures generated by turbocharged operation.
The fuel system is a mechanical direct injection system. An in-line
injection pump is mounted to the engine timing case and driven by a gear
from the camshaft. The pump generates high-pressure fuel pulses and
distributes them to each cylinder in the firing order (1-3-4-2). Fuel is
delivered from the pump to the injectors through steel high-pressure
lines. The injectors are of the multi-hole nozzle type, atomizing fuel
directly into the combustion bowl in the piston crown. A mechanical
governor is integral to the injection pump, maintaining engine speed
from no-load to full-load conditions.
The fuel system includes a fuel filter with a water separator. A manual
primer pump is located on the injection pump or fuel filter head to
bleed air from the system after filter changes. The engine is approved
for use with Hydrotreated Vegetable Oil (HVO) as a drop-in fuel
replacement for fossil diesel. Fuel consumption at the rated maximum
output of 3,300 rpm is 55.0 liters per hour (14.5 US gal/h). At a 2,400
rpm cruise setting, fuel consumption is approximately 22.0 liters per
hour (5.8 US gal/h). The engine should not be run continuously below its
torque band (2,200 rpm) to prevent cylinder glazing.
The lubrication system is a full-pressure, gear-type or trochoid pump
design. The oil pump is driven by the crankshaft or camshaft gear train.
Oil is drawn from the oil pan through a screened pickup and passed
through the pump before being routed through a full-flow spin-on oil
filter.
Pressurized oil travels to main galleries machined into the cylinder
block, delivering to the crankshaft main bearings and connecting rod
bearings through drilled passages. A separate oil passage directs
pressurized oil upward through the cylinder block and cylinder head to
the rocker shaft assembly. The system includes a pressure relief valve.
The system also supplies pressurized oil to the turbocharger bearing
housing through a dedicated feed line. A drain line returns oil from the
turbocharger to the crankcase.
The cooling system is an indirect freshwater (closed) cooling system
with a belt-driven seawater pump (rubber impeller type) and a
belt-driven freshwater circulation pump. Freshwater coolant is
circulated through the cylinder block and cylinder head. The freshwater
then passes through a heat exchanger, where seawater pumped from outside
the vessel absorbs heat from the freshwater before being discharged
overboard.
A wax-pellet thermostat, with an opening temperature of 71°C (160°F),
regulates freshwater coolant flow to maintain stable operating
temperatures. A seawater strainer is installed between the hull intake
and the seawater pump to prevent debris from entering the cooling
system. A zinc anode is installed in the heat exchanger or seawater
circuit to prevent galvanic corrosion. The freshwater pump is a genuine
Yanmar part with a replacement part number 119171-42004. The exhaust
elbow is manufactured from stainless steel and has an exhaust diameter
of 88.9 mm (3.5 in).
| Intake and Exhaust Systems |
Intake System: The intake system consists of a dry-type replaceable
paper air filter or a flame arrestor (marine requirement), a
turbocharger, an intercooler (charge air cooler), and a cast iron intake
manifold. The intercooler reduces intake air temperature after
turbocharger compression, increasing air density for improved combustion
efficiency.
Exhaust System: A cast iron exhaust manifold collects gases from all
four cylinders and feeds the turbocharger turbine inlet. The
turbocharger exhaust outlet is connected to a water-injected exhaust
elbow, where seawater is mixed with exhaust gases before discharge
through the vessel's exhaust hose and through-hull fitting. The exhaust
system operates at elevated temperatures; proper water flow is critical
to prevent overheating of the exhaust hose.
The engine is equipped with a 12-volt electrical system. The starter
motor is a 2.5 kW gear-reduction type. The alternator output is 80A. The
electrical system includes a key switch with pre-heat (glow plug)
position, warning buzzers and lamps for oil pressure and coolant
temperature, and a tachometer signal output from the alternator W
terminal.
Turbocharger System: The turbocharger is an oil-lubricated, water-cooled
bearing housing design. Engine oil pressure supplies lubrication to the
turbocharger shaft bearings. A wastegate controls maximum boost
pressure.
Transmission Options: The engine is compatible with multiple
transmission options. The KMH50A is a hydraulic multi-disc clutch
gearbox with an 8-degree down angle and a weight of 44 kg (97 lb). The
ZF63A is also a hydraulic multi-disc clutch gearbox with an 8-degree
down angle and a weight of 44 kg (97 lb). The engine is compatible with
the HSW630A1 Hurth marine gear. Installation length with this gear is
approximately 1,509 mm (59.4 in). Width is 665 mm (26.2 in) excluding
the alternator and mounting bracket.
Length, measured from the front pulley to the flywheel housing mounting
face, is 1,090 mm (42.9 in). Width, measured across the cylinder head
and intake manifold, is 710 mm (27.9 in). Height from the bottom of the
oil pan to the top of the valve cover is 780 mm (30.7 in). Dry weight of
the engine only (without transmission) is 418 kg (921 lb). Weight with a
marine gear is 436 kg (961 lb).
Oil Capacity: Total system capacity with filter change is dependent on
the oil pan configuration. Oil Change Interval: Under normal marine
service, the engine oil and filter should be changed every 250 operating
hours or annually, whichever comes first. Oil Filter: Spin-on full-flow
filter. Replacement interval coincides with each oil change. Fuel
Filters: Fuel filter with water separator. Replacement interval is 250
operating hours or annually. Fuel Filter Change Interval: 250 operating
hours or annually.
Seawater Pump Impeller: Replace every 500 operating hours or 2 years,
whichever comes first. Inspect annually. Valve Clearance (Cold): Adjust
with the engine at ambient temperature. Intake valve clearance is 0.20
mm (0.008 in). Exhaust valve clearance is 0.20 mm (0.008 in). Valve Lash
Adjustment Interval: Every 1,000 operating hours. Idle Speed: 700 rpm.
Injection Pump Timing: Static timing is set by shim adjustment. Factory
set; no field adjustment required.
Engine Coolant (Freshwater): Long-life antifreeze. Change interval is
1,000 operating hours or 2 years. Zinc Anode Replacement: Inspect and
replace the zinc anode in the heat exchanger and seawater circuit
annually or as needed based on corrosion. The original part number is
27210-200550. Air Filter (Flame Arrestor) Service: Clean with solvent
and re-oil (if oiled type) every 250 operating hours.
Anti-Siphon Valve Inspection: Inspect the anti-siphon valve in the
seawater cooling circuit every 500 operating hours to prevent seawater
backflow into the engine. Exhaust Elbow Inspection: Inspect the
water-injected exhaust elbow for carbon blockage and corrosion annually.
Replacement interval is 1,500 to 2,000 operating hours.
Cylinder Head Bolts, Stage one: 40 Nm (30 lb-ft).
Cylinder Head Bolts, Stage two: 80 Nm (59 lb-ft).
Cylinder Head Bolts, Stage three: 120 Nm (89 lb-ft).
Connecting Rod Bolts: 50 Nm (37 lb-ft).
Main Bearing Cap Bolts: 60 Nm (44 lb-ft).
Flywheel Housing to Cylinder Block Bolts: 50 Nm (37 lb-ft).
Flywheel to Crankshaft Bolts: 70 Nm (52 lb-ft).
Intake Manifold Nuts: 20 Nm (15 lb-ft).
Exhaust Manifold Nuts: 25 Nm (18 lb-ft).
Turbocharger Mounting Nuts: 40 Nm (30 lb-ft).
Turbocharger Oil Supply Line Fitting: 25 Nm (18 lb-ft).
Injection Pump Mounting Nuts: 25 Nm (18 lb-ft).
Injector Clamp Bolts: 30 Nm (22 lb-ft).
High-Pressure Fuel Line Nuts: 25 Nm (18 lb-ft).
Glow Plugs: 15 Nm (11 lb-ft).
Valve Cover Bolts: 10 Nm (7 lb-ft).
Oil Pan Bolts: 15 Nm (11 lb-ft).
Oil Filter (Spin-On): 15 Nm (11 lb-ft) or 3/4 turn after gasket contact.
Freshwater Pump Mounting Bolts: 20 Nm (15 lb-ft).
Seawater Pump Mounting Bolts: 15 Nm (11 lb-ft).
Thermostat Housing Bolts: 10 Nm (7 lb-ft).
Heat Exchanger Mounting Bolts: 15 Nm (11 lb-ft).
Crankshaft Pulley Bolt: 150 Nm (111 lb-ft).
Starter Motor Mounting Bolts: 40 Nm (30 lb-ft).
Alternator Pivot and Adjustment Bolts: 25 Nm (18 lb-ft).
The Yanmar 4LH-STE engine was utilized almost exclusively as a marine
propulsion engine for powerboats, offshore cruisers, and light
commercial vessels.
Powerboat Applications:
Planing powerboats (25 to 40 feet in length).
Fast cruisers.
Day boats.
Rigid inflatable boats (RIB) with inboard diesel configurations.
Offshore Cruiser Applications:
Offshore cruising yachts (power and sail).
Long-range cruisers requiring high power density.
Semi-displacement hulls.
Light Commercial Applications:
Small fishing vessels.
Patrol boats.
Workboats.
Tenders for larger commercial vessels.
Sailboat Applications:
Larger performance sailboats requiring high auxiliary power.
Ocean-going sailing yachts using the SD-series saildrive option.
Other Applications:
Small generator sets (limited production).
Industrial power units.
The 4LH-STE remains in current production, with continuing parts
availability through Yanmar's global marine dealer network. Its
combination of high power output, compact dimensions, low weight, and
HVO fuel compatibility makes it a preferred engine for vessel owners
requiring a reliable, powerful, and environmentally conscious diesel
powerplant.
Transmission Data: KMH50A: Hydraulic multi-disc clutch gearbox with an
8-degree down angle. Weight: 44 kg (97 lb). Suitable for shaft drive
installations. ZF63A: Hydraulic multi-disc clutch gearbox by ZF Marine
with an 8-degree down angle. Weight: 44 kg (97 lb). Suitable for shaft
drive installations. HSW630A1 Hurth: Marine gear compatible with the
4LH-STE. Installation length with this gear is 1,509 mm (59.4 in). Width
excluding alternator and mounting bracket is 665 mm (26.2 in).
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