Yanmar 6BY-260 Specifications
| Engine Model: Yanmar 6BY-260 |
| Engine Type: 4-stroke inline 6-cylinder turbocharged water-cooled diesel |
| Total Displacement: 183 cu.in (2.99 L) |
| Rated Engine Power: 260 Hp (191 kW) at 4000 rpm |
| Fuel System Type: Common rail direct injection |
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The Yanmar 6BY-260 is a high-performance,
inline 6-cylinder marine diesel engine developed in collaboration with
the BMW Group. Introduced in the mid-2000s, this powerplant represents a
departure from conventional marine diesel designs, leveraging
automotive-derived common rail technology to deliver high power output
from a compact displacement. The Yanmar 6BY-260 was engineered
specifically for planing hulls, including express cruisers, sportfishing
vessels, and large tenders, where power-to-weight ratio is critical.
The engine line evolved through several variants, including the 6BY2-260
and the later 6BY3-260, each incorporating refinements in emissions
compliance, electronic control systems, and marinisation components. The
"Z" suffix indicates a sterndrive configuration for use with Z-drive
systems rather than conventional shaft drives. With a dry weight of
approximately 328 kg (723 lb) and a maximum rating of 260 mhp at 4,000
rpm, the 6BY series provides a level of performance that competes with
gasoline engines while delivering the durability and fuel efficiency of
diesel.
The Yanmar 6BY-260 is distinguished by its unusually low displacement
for a 260 hp 6-cylinder diesel. Displacing only 2.993 liters from a bore
and stroke of 84 mm by 90 mm, the engine relies on high-pressure common
rail direct injection and aggressive turbocharging to achieve its
specific output of 87 hp per liter. The Bosch common rail system
delivers fuel at pressures sufficient for complete combustion across the
operating range, while a turbocharger with charge air cooling ensures
dense intake air for power generation. The engine utilizes a DOHC
24-valve cylinder head, a configuration uncommon in marine diesels of
this size, contributing to its high-rpm capability.
A freshwater cooling system with a separate seawater pump provides
corrosion resistance in marine environments. The 6BY-260 meets stringent
emissions standards including US EPA Tier 3, EU RCD, and BSO II,
achieved through precise electronic fuel control rather than complex
exhaust aftertreatment. The engine is controlled via NMEA 2000 certified
CAN bus electronics, enabling integration with modern vessel management
systems. Service intervals are extended compared to older marine
diesels, though the engine demands strict adherence to maintenance
schedules for its high-pressure fuel system.
Engine Type: Inline 6-cylinder, 4-stroke, turbocharged diesel,
longitudinal mounting
Displacement: 2.993 L (183 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, Bosch Common Rail System
Aspiration: Turbocharged and intercooled
Firing Order: 1-5-3-6-2-4
Direction of Rotation: Counter-clockwise (viewed from flywheel)
Max Output (MCR): 191 kW (260 hp; 256 bhp) @ 4,000 rpm
Continuous Rating: 147 kW (198 hp; 195 bhp) @ 3,600 rpm
Max Torque: 540 Nm (398 lb-ft) @ 2,200-2,800 rpm
Idle Speed: Adjustable 650-950 rpm
The cylinder block is constructed from high-strength cast iron with an
inline 6-cylinder configuration. An open-deck design is used, with the
crankcase integrated into the block casting. The cylinder bores are
machined directly into the parent cast iron material, eliminating
separate liners.
Seven main bearing caps support the crankshaft, providing rigidity
necessary for the high specific output. The water jacket surrounds the
cylinders fully. The block incorporates piston cooling oil nozzles,
which are critical for managing thermal loads at maximum power output.
The cylinder head is a single casting in aluminum alloy, a choice that
reduces overall engine weight and improves heat dissipation compared to
cast iron. The DOHC valvetrain operates four valves per cylinder for a
total of 24 valves. The camshafts are driven by a timing chain.
Valve actuation utilizes roller finger followers with hydraulic lash
adjusters, eliminating manual valve clearance adjustments. The pent-roof
combustion chamber centers the fuel injector for optimal mixture
formation. The glow plug system provides cold-start assistance,
controlled automatically by the electronic control unit.
Valves: 24 total (12 intake, 12 exhaust)
Intake Valve Diameter: 29.0 mm (1.14 in)
Exhaust Valve Diameter: 25.5 mm (1.00 in)
Valve Stem Diameter: 6.0 mm (0.24 in)
Valve Seat Material: High-strength alloy steel inserts
Valve Clearance: Hydraulic lash adjusters - no manual adjustment
The fuel system is a third-generation common rail direct injection
system supplied by Bosch. A high-pressure fuel pump draws fuel from the
tank and pressurizes it to a maximum of 1,600 bar (23,206 psi). This
pressurized fuel is stored in a common rail accumulator mounted on the
engine. From the rail, fuel is delivered to solenoid-type injectors that
protrude directly into the combustion chamber.
The injection strategy employs multiple events per cycle - including
pilot injection and main injection - to control combustion noise and
reduce emissions. The fuel system includes a fuel cooler and a water
separator. The engine management system continuously adjusts injection
timing and fuel quantity based on load and speed demands.
The lubrication system is a pressurized, wet-sump design with a
gear-type oil pump driven from the crankshaft. The pump draws oil from a
fabricated steel or aluminum oil pan through a screened pickup tube. A
full-flow, spin-on oil filter is mounted externally on the engine block.
An integrated oil cooler, using engine coolant, maintains oil
temperature under sustained high-load operation. Piston cooling nozzles
direct oil jets at the underside of each piston for thermal management.
Oil Capacity (including filter): 9.0 L (9.5 US qt)
Oil Pressure at 3,000 rpm: 400-500 kPa (58-72 psi)
Recommended Oil Viscosity: 5W-30 or 10W-40, meeting API CI-4 or higher
Oil Pump Type: Gear-type, crankshaft-driven
The cooling system is a closed-loop, pressurized freshwater (coolant)
design with a belt-driven centrifugal pump. A separate rubber-impeller
seawater pump draws raw water from the environment, which then passes
through a heat exchanger to transfer heat from the freshwater circuit.
This dual-circuit design protects the engine block and cylinder head
from seawater corrosion.
A wax-type thermostat maintains freshwater operating temperature between
75-85 °C (167-185 °F). A charge air cooler (intercooler) uses seawater
or freshwater to reduce intake air temperature after turbocharging. The
exhaust mixing elbow injects seawater into the exhaust stream to cool
exhaust gases before discharge.
| Intake and Exhaust Systems |
Intake System: A cast aluminum intake manifold distributes air to the
cylinders. A charge air cooler (intercooler) reduces intake air
temperature after compression, increasing air density for improved
combustion.
Exhaust System: A cast iron exhaust manifold routes gases to the
turbocharger. A water-injected exhaust elbow cools exhaust gases to safe
temperatures for onboard exhaust hose systems. An exhaust temperature
sensor monitors system operation.
The engine utilizes a 12V DC electrical system with a 2.0 kW electric
starter motor and a high-output 150A alternator. The alternator provides
sufficient capacity for vessel house loads in addition to engine
operation.
Turbocharging System: A fixed geometry turbocharger with wastegate
provides boost pressure. The turbocharger is mounted to the exhaust
manifold and includes a water-cooled bearing housing for durability.
Boost pressure is managed by the engine ECU via a wastegate actuator.
Control System: The engine incorporates a CAN bus electronic control
system compliant with NMEA 2000 standards. Digital instrumentation and
vessel management system integration is supported. Electronic throttle
and shift controls are available, with redundancy for critical
functions.
Emissions Control: The engine meets US EPA Tier 3, EU RCD (Recreational
Craft Directive), and BSO II emission standards through precise
electronic fuel control and combustion optimization.
Overall Length (with KMH gearbox): 1,069 mm (42.1 in)
Overall Width: 762 mm (30.0 in)
Overall Height: 717 mm (28.2 in)
Dry Weight (6BY3 without gear): 328 kg (723 lb)
Dry Weight (6BY2 without gear): 315 kg (694 lb)
Sterndrive Model Length: 1,027 mm (40.4 in)
Valve Clearance: Hydraulic lash adjusters - no manual adjustment
required.
Engine Oil Change Interval: 250 hours or annually, whichever occurs
first.
Oil Filter Replacement: With every oil change.
Fuel Filter Replacement: 250 hours or annually.
Seawater Pump Impeller Replacement: 200 hours or annually.
Timing Chain Inspection: 1,000 hours; no scheduled replacement interval.
Coolant Replacement Interval: 500 hours or 2 years.
Valve Clearance Inspection: Not required due to hydraulic lash
adjusters.
Fuel Injection System Service: Every 1,000 hours.
Cylinder Head Bolts (Stage 1): 30 Nm (22 lb-ft).
Cylinder Head Bolts (Stage 2): 90 Nm (66 lb-ft).
Connecting Rod Cap Bolts: 40 Nm (30 lb-ft).
Main Bearing Cap Bolts: 100 Nm (74 lb-ft).
Flywheel Bolts: 80 Nm (59 lb-ft) + 90° angle.
High-Pressure Fuel Pump Mounting Bolts: 25 Nm (18 lb-ft).
Common Rail Mounting Bolts: 25 Nm (18 lb-ft).
Injector Clamp Bolts: 12 Nm (9 lb-ft).
Intake Manifold Bolts: 20 Nm (15 lb-ft).
Exhaust Manifold Nuts: 30 Nm (22 lb-ft).
Turbocharger Mounting Nuts: 45 Nm (33 lb-ft).
Turbocharger Oil Feed Line: 30 Nm (22 lb-ft).
The Yanmar 6BY-260 engine was utilized across a variety of marine vessel
types, primarily in planing hull applications requiring high power
output from a lightweight, compact diesel powerplant.
Express Cruisers and Sportfishing Boats: The 6BY-260 was installed as
twin-engine configurations in vessels such as the Albemarle 280 Express
Fisherman, Luhrs 28 Open, and Brandaris 1100 Pur Sang. Twin
installations produce 520 total horsepower.
Tenders and Dayboats: Pascoe Custom 9.6 tenders utilized twin 6BY-260
engines coupled to Yanmar ZT370 duoprop sterndrives.
Trawlers and Cruisers: Ranger Tugs R-29 models employed single 6BY-260
installations for extended-range cruising.
Workboats and Patrol Vessels: The engine was selected for various
commercial applications including fishing vessels, pilot boats, and
patrol craft requiring reliable high-speed operation.
Yacht Auxiliary Power: The 6BY-260 was installed as auxiliary power in
larger yachts and as a generator drive engine for marine power
generation applications.
Transmission and Drive System Compatibility - KMH50A / KMH51A: Hydraulic
marine gears with 8° down angle for conventional shaft drive
installations. ZT350 / ZT370: Yanmar steerable Z-drives with duoprop
(twin counter-rotating propeller) configuration for sterndrive
applications. The "Z" suffix in 6BY3-260Z denotes this configuration.
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