Yanmar 4BY2-180 Specifications
| Engine Model: Yanmar 4BY2-180 |
| Engine Type: 4-stroke inline 4-cylinder turbocharged water-cooled diesel |
| Total Displacement: 122 cu.in (1.99 L) |
| Rated Engine Power: 180 Hp (132 kW) at 4000 rpm |
| Fuel System Type: Common rail direct injection |
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The Yanmar 4BY2-180 is an inline four-cylinder
marine diesel engine featuring common-rail direct injection,
turbocharging, and a charge air intercooler. Designed as the
higher-output variant within the 4BY2 series, this engine represents
Yanmar’s application of automotive-grade diesel technology to the marine
propulsion sector. The 4BY2 series improved upon the original 4BY
platform through enhanced fuel filtration, a redesigned oil separator,
and refined electronic engine management.
The engine’s architecture centers on a compact inline four-cylinder
configuration with a displacement of 2.0 liters, achieving a specific
output of 90 hp per liter through the combination of high-pressure
common-rail injection and forced induction. The common-rail system
operates at pressures up to 1,800 bar (26,100 psi), delivering precise
fuel metering across multiple injection events per combustion cycle.
This technology reduces combustion noise, lowers emissions, and improves
fuel efficiency compared to mechanically governed injection systems. The
turbocharger, paired with a seawater-cooled intercooler, maintains
charge air density under sustained high-load operation.
Freshwater cooling with a heat exchanger isolates the engine block from
corrosive seawater, while the closed-loop lubrication system
incorporates an oil cooler to manage thermal loads. The 4BY2-180 is
controlled by a Yanmar CAN-bus electronic management system, providing
single-lever throttle and shift operation, engine synchronization for
twin installations, and diagnostic interface connectivity. The engine
gained acceptance in planing powerboats, displacement cruisers, and
light commercial vessels where a balance of power density and fuel
economy is required.
Engine Type: Vertical inline 4-cylinder, 4-cycle, turbocharged,
water-cooled diesel.
Displacement: 1.995 L (122 cu.in).
Bore: 84.0 mm (3.31 in).
Stroke: 90.0 mm (3.54 in).
Compression Ratio: 16.5:1.
Combustion System: Direct injection with common-rail fuel system.
Firing Order: 1-3-4-2.
Maximum Power (intermittent, crankshaft): 132 kW (180 hp) @ 4,000 rpm.
Continuous Power (crankshaft): 102 kW (137 hp) @ 3,600 rpm.
Maximum Torque: 350 Nm (258 lb-ft) @ 2,000-2,500 rpm.
Idle Speed: 700 rpm.
Rotation Direction: Counter-clockwise when viewed from the flywheel end.
The cylinder block is manufactured from cast aluminum alloy using
high-pressure die-casting techniques. This material selection reduces
overall engine mass to 258 kg (569 lb) dry, a significant weight saving
compared to cast iron equivalents. The block incorporates a closed-deck
design for enhanced cylinder rigidity under the elevated combustion
pressures generated by common-rail injection and turbocharging.
Cylinder bores are cast-in-place iron liners, centrifugally cast and
machined to final specification. The liners are replaceable, allowing
for engine overhaul without block replacement. Bore diameter measures
84.0 mm (3.31 in) with a piston stroke of 90.0 mm (3.54 in), yielding a
total displacement of 1.995 L (122 cu.in). This under-square
bore-to-stroke ratio of 0.933 favors low-end torque generation, aligning
with marine propulsion requirements where sustained operation at
moderate engine speeds is standard.
The crankshaft is forged from chromium-molybdenum steel with
induction-hardened journal surfaces. Five main bearings support the
crankshaft. Thrust washers positioned at the center main bearing control
axial crankshaft play. Connecting rods are forged from high-carbon steel
with a fracture-split big end design. Pistons are cast aluminum with a
low-expansion silicon alloy, featuring two compression rings and one oil
control ring. The piston crown incorporates a re-entrant combustion bowl
designed for the common-rail injection spray pattern.
Oil squirters are integrated into the cylinder block, directing
pressurized oil to the underside of each piston crown. These jets are
essential for managing thermal loads under sustained high-output
operation, particularly during planing mode operation at 3,500-4,000
rpm.
The cylinder head is manufactured from aluminum alloy with a cross-flow
design positioning intake ports on the inlet side and exhaust ports on
the exhaust side. The combustion chambers are of the pent-roof
configuration with four valves per cylinder and a centrally located fuel
injector.
Each cylinder head contains 16 valves: eight intake valves and eight
exhaust valves. Intake valve diameter measures 30.0 mm (1.18 in), while
exhaust valve diameter measures 26.0 mm (1.02 in). Valve stem diameter
is 6.0 mm (0.24 in) for both intake and exhaust. The valvetrain utilizes
roller rocker arms and hydraulic lash adjusters, eliminating the need
for periodic valve clearance adjustments.
The camshafts are driven by a silent-type timing chain with a pitch of
8.0 mm (0.31 in). The chain routes from the crankshaft sprocket to the
exhaust camshaft sprocket, with a second chain segment connecting the
exhaust camshaft to the intake camshaft. An automatic hydraulic
tensioner maintains consistent chain tension throughout the engine’s
service life. The timing chain is designed for the life of the engine
under normal operating conditions.
The Yanmar 4BY2-180 employs a common-rail direct injection system
operating at high pressure. A high-pressure pump, driven by the timing
chain, supplies fuel to the common rail accumulator. The pump is a
radial piston type with quantity control, delivering only the fuel
volume required for current operating conditions. Fuel rail pressure is
regulated up to 1,800 bar (26,100 psi) under high-load conditions.
The injectors are solenoid-actuated units with multi-hole nozzles.
Multiple injection events per combustion cycle - including pilot
injection, main injection, and post-injection - are utilized to reduce
combustion noise, lower NOx and particulate emissions, and enable
smoother engine operation.
The injection timing and fuel quantity are controlled by the engine
control unit based on inputs from the crankshaft position sensor,
camshaft position sensor, rail pressure sensor, coolant temperature
sensor, intake air temperature sensor, boost pressure sensor, and
throttle position sensor. The fuel system incorporates a primary fuel
filter with water separator and a secondary high-efficiency cartridge
filter. A hand primer is provided for system priming after filter
replacement.
The lubrication system utilizes a forced-feed, full-flow design with a
gear-type oil pump mounted to the front of the crankshaft. A pressure
relief valve integrated into the pump maintains system pressure within
design parameters.
Total oil capacity is 8.5 L (9.0 qt). Recommended oil viscosity is SAE
5W-40 or 10W-40 meeting BMW Longlife-04 or ACEA C3 specifications. These
low-ash formulations are required for compatibility with the diesel
particulate filter where equipped. Oil pressure specifications require a
minimum of 1.0 bar (15 psi) at warm idle and 4.0-5.0 bar (58-73 psi) at
3,000 rpm.
The oil filter is a spin-on, full-flow type mounted to the cylinder
block. A liquid-to-oil plate-type oil cooler is integrated into the
lubrication system, utilizing engine coolant to stabilize oil
temperature. The oil pan is cast aluminum with internal baffling and a
sump designed for operation at vessel trim angles up to 15 degrees
continuous and 25 degrees intermittent.
The cooling system is a closed-loop freshwater system with a heat
exchanger for seawater cooling. A centrifugal water pump, driven by the
accessory drive belt, circulates fresh water through the cylinder block,
cylinder head, and oil cooler. A seawater pump, mounted on the front of
the engine, draws raw water through a through-hull fitting and strainer,
then circulates it through the heat exchanger and the charge air
intercooler before discharging to the exhaust injection elbow.
The thermostat is a wax-pellet unit with an opening temperature of 82-86
°C (180-187 °F). A bypass circuit allows freshwater circulation within
the engine during warm-up. Total freshwater coolant capacity is 7.0 L
(7.4 qt). The heat exchanger is a shell-and-tube design with a
seawater-cooled tube bundle. Zinc anodes are installed in the seawater
circuit to prevent galvanic corrosion. System pressure is controlled by
a pressure cap rated at 1.0 bar (15 psi) on the freshwater fill neck.
The exhaust manifold is manufactured from cast iron with a water-cooled
jacket. Seawater is injected into the exhaust stream at the turbocharger
outlet to cool exhaust gases before they enter the rubber exhaust hose
and gooseneck fitting.
The engine is equipped with a 12-volt alternator rated at 150 amperes
(high output), driven by a poly-V belt from the crankshaft pulley. The
starting system includes a 2.0 kW electric starter motor with a sealed
construction for marine environment protection.
Aspiration System: The 4BY2-180 is equipped with a fixed geometry
turbocharger manufactured by Mitsubishi or BorgWarner. Maximum boost
pressure ranges from 1.4-1.8 bar (20-26 psi) absolute depending on
engine speed and load. A seawater-cooled charge air intercooler
(aftercooler) reduces intake air temperature by 50-70 °C (90-126 °F)
under sustained boost conditions, increasing charge density and reducing
thermal stress on the combustion system. The intercooler is a
tube-and-shell design integrated into the seawater cooling circuit.
Engine Management: The Yanmar CAN-bus electronic control system
integrates control of fuel injection, boost pressure, idle speed,
cooling system operation, and diagnostic monitoring. The system provides
single-lever throttle and shift control on vessels equipped with Yanmar
electronic controls. For twin-engine installations, the CAN-bus system
enables synchronization of engine speed and load management. A dedicated
marine instrument panel displays engine speed, coolant temperature, oil
pressure, fuel consumption rate, battery voltage, and diagnostic fault
codes.
Crankcase Ventilation: A closed-loop crankcase ventilation system routes
blow-by gases from the valve cover through a redesigned oil separator,
which returns condensed oil to the sump while directing vapor to the
intake system upstream of the turbocharger compressor inlet. The 4BY2
series oil separator features improved efficiency compared to the
original 4BY design.
Overall Length (without gearbox): 755 mm (29.7 in) measured from front
pulley face to flywheel housing flange.
Overall Width: 620 mm (24.4 in).
Overall Height: 685 mm (27.0 in) from oil pan bottom to engine top.
Dry Weight (without gearbox): 258 kg (569 lb).
Gearbox Options: Yanmar KMH series or ZF Marine series transmissions,
adding 35-65 kg (77-143 lb) depending on model.
Timing Chain: Designed for engine life under normal operating
conditions. Inspection recommended at 1,000 operating hours. Fuel Filter
Replacement Interval: 250 operating hours or 12 months for primary
filter; 500 operating hours for secondary filter. Valve Inspection:
Every 800 operating hours. Charge Air Intercooler Cleaning Interval: 500
operating hours more frequent in silty or tropical waters.
Heat Exchanger Zinc Anode Inspection: 250 operating hours. Replacement
when 50 percent consumed. Engine Oil Change Interval: 250 operating
hours or 12 months, whichever occurs first. Yanmar recommends oil
sampling analysis for extended intervals beyond 250 hours. Oil Filter
Replacement Interval: Replace with every oil change.
Coolant Change Interval: 500 operating hours or 24 months. Seawater Pump
Impeller Inspection Interval: 200 operating hours. Replacement interval:
500 operating hours or 24 months. Compression Pressure: Minimum 2.8 MPa
(406 psi) with no cylinder varying more than 0.3 MPa (44 psi) from
others. Injector Testing Interval: Every 800 operating hours.
Cylinder Head Bolts, Step 1: 30 Nm (22 lb-ft).
Cylinder Head Bolts, Step 2: 60 Nm (44 lb-ft) plus 90° rotation.
Crankshaft Damper Pulley Bolt: 200-210 Nm (148-155 lb-ft).
Connecting Rod Cap Bolts: 35-40 Nm (26-30 lb-ft) plus 90° rotation.
Main Bearing Cap Bolts: 60-65 Nm (44-48 lb-ft) plus 90° rotation.
Flywheel Bolts: 90-100 Nm (66-74 lb-ft).
Camshaft Sprocket Bolts: 50-60 Nm (37-44 lb-ft).
Camshaft Bearing Cap Bolts: 20-25 Nm (15-18 lb-ft).
Valve Cover Bolts: 8-10 Nm (6-7 lb-ft).
Intake Manifold Bolts: 18-22 Nm (13-16 lb-ft).
Exhaust Manifold Nuts: 25-30 Nm (18-22 lb-ft).
Turbocharger Mounting Nuts: 35-40 Nm (26-30 lb-ft).
Turbocharger Oil Feed Line: 20-25 Nm (15-18 lb-ft).
Turbocharger Coolant Lines: 25-30 Nm (18-22 lb-ft).
Oil Pan Bolts: 8-12 Nm (6-9 lb-ft).
Timing Chain Tensioner: 20-25 Nm (15-18 lb-ft).
Timing Chain Guide Bolts: 10-12 Nm (7-9 lb-ft).
Water Pump Mounting Bolts (freshwater): 15-20 Nm (11-15 lb-ft).
Seawater Pump Mounting Bolts: 15-20 Nm (11-15 lb-ft).
Thermostat Housing Bolts: 8-12 Nm (6-9 lb-ft).
Heat Exchanger Mounting Bolts: 20-25 Nm (15-18 lb-ft).
Common Rail Mounting Bolts: 20-25 Nm (15-18 lb-ft).
High-Pressure Fuel Pump Mounting Bolts: 25-30 Nm (18-22 lb-ft).
Fuel Injector Clamp Bolts: 25-30 Nm (18-22 lb-ft).
Glow Plugs: 15-20 Nm (11-15 lb-ft).
Crankshaft Position Sensor Mounting Bolt: 8-10 Nm (6-7 lb-ft).
Camshaft Position Sensor Mounting Bolts: 8-10 Nm (6-7 lb-ft).
Oxygen Sensors (if equipped): 40-45 Nm (30-33 lb-ft).
Alternator Mounting Bracket Bolts: 25-30 Nm (18-22 lb-ft).
Starter Motor Mounting Bolts: 35-40 Nm (26-30 lb-ft).
Engine Mounts (to block): 50-55 Nm (37-41 lb-ft).
Recreational Powerboats: The 4BY2-180 is installed as primary propulsion
in planing powerboats from 6 to 9 meters (20-30 feet) in length,
including center consoles, walkaround cuddy cabins, and deck boats. The
engine provides the power density required for planing speeds while
maintaining fuel economy at cruising speeds. Applications include hull
designs from Boston Whaler, Grady-White, Robalo, and Scout.
Small Cabin Cruisers: Express cruisers and weekender models up to 8.5
meters (28 feet) receive the 4BY2-180 in single-engine or twin-engine
configurations. The common-rail engine’s low vibration and noise
characteristics enhance onboard comfort during overnight use.
Manufacturers include Beneteau, Jeanneau, Monterey, and Four Winns.
Downeast and Pilot House Boats: Semi-displacement hull designs from
builders such as Eastern, Parker, and Steiger Craft utilize the 4BY2-180
for its combination of low-end torque and moderate rpm cruising
capability. The engine’s continuous rating of 137 hp at 3,600 rpm
matches the power requirements of these hull forms.
Light Commercial Vessels: Patrol boats, pilot launches, and small
workboats operate the 4BY2-180 in applications requiring high
reliability and extended service intervals. The Yanmar CAN-bus
diagnostic interface simplifies fleet management and maintenance
tracking.
Yacht Tenders and Chase Boats: Large yachts and megayachts deploy the
4BY2-180-powered tenders and chase boats, where compact dimensions and
low dry weight facilitate safe launching and retrieval from davits. The
common-rail engine’s cold-start capability and electronic throttle
response suit the operational requirements of yacht tender service.
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