Yanmar 4LV250 Specifications
| Engine Model: Yanmar 4LV250 |
| Engine Type: 4-stroke inline 4-cylinder turbocharged water-cooled diesel |
| Total Displacement: 168 cu.in (2.75 L) |
| Rated Engine Power: 250 Hp (184 kW) at 3800 rpm |
| Fuel System Type: Common rail direct injection |
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The Yanmar 4LV250 is the flagship high-output
model of the 4LV common rail series, a four-stroke, vertical,
water-cooled diesel engine introduced to deliver maximum torque and
power from a compact 2.75 liter block. Released in 2017 as a successor
to the 4LH and 4/6BY series, this engine was developed to serve both
light-duty commercial and pleasure marine applications, including large
sailing yachts, fast motorboats, and high-end tenders.
The Yanmar 4LV250 distinguishes itself through a combination of a
turbocharger, a charge-air cooler (intercooler), and a Denso common rail
direct injection system. This configuration enables a flat torque curve
from 2,000 to 3,000 rpm, providing power characteristics comparable to
larger displacement engines while maintaining a lightweight and compact
footprint. The engine meets US EPA Tier 3 and EU RCD 2 emission
standards and is approved for HVO (Hydrotreated Vegetable Oil) fuel.
The Yanmar 4LV250 is an inline, four-cylinder diesel engine that
utilizes a long-stroke architecture with a stroke exceeding the bore by
11.6 mm. This configuration prioritizes high torque output at low engine
speeds, which is essential for marine propulsion. The engine management
system is a full electronic control unit governing the common rail
injection system, and it supports NMEA 2000 and J1939 data bus protocols
for integration with vessel control systems.
Engine Type: Vertical, 4-stroke, water-cooled diesel
Number of Cylinders: 4, inline
Displacement: 2.755 L / 168.0 cu.in
Bore x Stroke: 92.0 mm x 103.6 mm / 3.62 in x 4.08 in
Compression Ratio: 15.0:1
Combustion System: Direct Injection, Denso Common Rail System
Aspiration: Turbocharged and intercooled
Rated Output: 184 kW / 250 hp at 3,800 rpm
Maximum Torque: 560 Nm / 413 lb-ft at 2,000-3,000 rpm
Idle Speed: 700 rpm
Dry Weight (Bobtail, without gear): 334 kg / 736 lbs
Engine Oil Capacity: 8.5 L / 9.0 US qt
Fuel Consumption (Max): 53.0 L/h / 14.0 GPH at 3,800 rpm
Electrical System: 12V DC starting motor (2.0 kW); Alternator: 12V -
130A (Denso)
Certifications: RCD 2, IMO Tier 2, EPA Tier 3, BSO II, EMC, SOLAS
The cylinder block is constructed from high-strength cast iron,
utilizing a design derived from automotive diesel engines but marinized
specifically for marine conditions. The block features a deep-skirt
configuration for enhanced structural rigidity under torsional load. The
cylinder bores are machined with a plateau-honed finish. Within the
block, a forged steel crankshaft is supported by five main bearings.
The connecting rods are forged steel, designed for the high cylinder
pressures generated by the 15.0:1 compression ratio and turbocharging.
The pistons are aluminum alloy castings with a complex crown geometry
optimized for the direct injection swirl. Each piston is cooled by an
oil jet directed from the block to manage the thermal stress of
high-output continuous operation.
The cylinder head is a cross-flow cast iron design, chosen for its
thermal stability under sustained high load. It houses four valves per
cylinder and the common rail injectors. The valve mechanism is driven by
a gear train or chain drive from the crankshaft, utilizing roller rocker
arms to reduce frictional losses.
Valve Configuration: 4 valves per cylinder, 16 valves total
Valve Clearance: Hydraulic lash adjusters (no manual adjustment
required)
Valve Timing: Fixed timing optimized for low-end torque and high RPM
power delivery
The 4LV250 employs a full electronic control Denso common rail system. A
high-pressure supply pump delivers fuel to a common rail accumulator
mounted on the cylinder head at pressures up to 2,000 bar / 29,000 psi.
The rail distributes fuel to injectors featuring a multi-hole nozzle.
The engine control unit manages injection timing, duration, and
pressure, enabling multiple injection events per combustion cycle. These
events include pilot injection to reduce combustion noise, main
injection for power, and post-injection strategies for thermal
management. The system is approved for HVO fuel.
Lubrication is provided by a forced circulation system using a trochoid
pump, known for its compact efficiency. The pump draws oil from the sump
and forces it through a full-flow spin-on filter before distributing it
to the crankshaft, connecting rod bearings, camshaft, and turbocharger.
An oil cooler is integrated into the system, utilizing the freshwater
cooling circuit to stabilize oil temperature.
The cooling system is a dual-circuit design. A freshwater (closed)
circuit circulates coolant through the cylinder block, cylinder head,
turbocharger, and oil cooler via a belt-driven centrifugal pump. Heat is
transferred from the freshwater circuit to the raw (seawater) circuit
through a plate-type heat exchanger.
The raw water circuit, driven by a rubber impeller pump, draws seawater
to cool the heat exchanger and the charge-air cooler before being
discharged into the exhaust elbow. This system maintains consistent
operating temperatures regardless of seawater conditions.
| Intake and Exhaust Systems |
Intake System: The intake system incorporates a heavy-duty air cleaner.
The charge-air cooler (intercooler) reduces the temperature of the
compressed intake air after the turbocharger, increasing air density for
improved combustion efficiency and power output.
Exhaust System: The engine is supplied with an exhaust mixing elbow
(L-type or high-riser) where seawater is injected to cool the exhaust
gases before they enter the rubber exhaust hose.
Timing System: The camshaft and injection pump are driven by a gear
train from the crankshaft. This industrial design provides precise
timing and eliminates the belt replacement intervals common in
automotive engines.
Emission Control: The engine meets EPA Tier 3 and RCD 2 standards
through internal engine design and precise electronic fuel control. No
selective catalytic reduction (SCR) or Diesel Particulate Filter (DPF)
is required for these certifications.
Control System: The engine is compatible with Yanmar VC10, VC20, or VC30
Vessel Control Systems, featuring mechanical throttle sensors,
electronic monitoring, and joystick control options for inboard and
sterndrive configurations.
Overall Length (including KMH50A gear): 1,151 mm / 45.3 in
Overall Width: 755 mm / 29.7 in
Overall Height: 772 mm / 30.4 in
Dry Weight (Bobtail): 334 kg / 736 lbs
Dry Weight (with KMH50A 8° down-angle gear): 384 kg / 847 lbs
Dry Weight (with V-drive): 407 kg / 897 lbs
Engine Oil: Use 15W-40 or 5W-30 diesel oil meeting API CK-4 or CJ-4.
Engine Oil and Filter: Replace every 250 hours or annually.
Raw Water Pump Impeller: Inspect annually.
Raw Water Pump Impeller: Replace every 1-2 years.
Fuel Filters: Replace primary and secondary filters every 250 hours.
Valve Clearance: Inspection is not required due to hydraulic lash
adjusters.
Coolant Type: Use ethylene glycol antifreeze with corrosion inhibitors.
Cooling System: Replace coolant every 1,000 hours or 2 years.
Drive Belt: Inspect every 250 hours; replace if cracking or glazing is
evident.
Zinc Anodes: Inspect and replace annually.
Cylinder Head Bolts, Step 1: 40 Nm (30 lb-ft)
Cylinder Head Bolts, Step 2: 80 Nm (59 lb-ft)
Main Bearing Cap Bolts: 90 Nm (66 lb-ft)
Connecting Rod Cap Bolts: 45 Nm (33 lb-ft)
Camshaft Bearing Cap Bolts: 25 Nm (18 lb-ft)
Intake Manifold Bolts: 20 Nm (15 lb-ft)
Exhaust Manifold Nuts: 25 Nm (18 lb-ft)
Turbocharger Mounting Nuts: 35 Nm (26 lb-ft)
Injector Clamp Bolts: 15 Nm (11 lb-ft)
High-Pressure Pump Mounting Bolts: 22 Nm (16 lb-ft)
Oil Pan Bolts: 12 Nm (9 lb-ft)
Valve Cover Bolts: 10 Nm (7 lb-ft)
Crankshaft Pulley Bolt: 200 Nm (148 lb-ft)
Flywheel (Flex Plate) Bolts: 120 Nm (89 lb-ft)
Marine Gear to Flywheel Housing Bolts: 80 Nm (59 lb-ft)
The 4LV250 engine is exclusively used in marine applications, serving as
a propulsion unit for various vessels and sterndrive systems.
Aspen Power Catamarans C100: The 4LV250 is the standard engine for this
power catamaran model, achieving 4.1 mpg at 18 mph (32% efficiency
improvement over previous configurations).
Inboard Propulsion (KMH50A Gear): Standard configuration with an 8°
down-angle transmission for shaft drive systems.
V-Drive Propulsion (KMH50V Gear): Configuration with a 12° shaft angle,
designed for space-constrained engine rooms.
Sterndrive (ZT370): Designated as the 4LV250Z for sterndrive
applications featuring hydraulic shifting.
Motor Yachts and Cruisers: Used in various fast motorboats, fishing
boats, and rescue boats within the 110-180 kW power range.
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