Yanmar 6LYA STE Specifications
| Engine Model: Yanmar 6LYA STE |
| Engine Type: 4-stroke inline 6-cylinder turbocharged water-cooled diesel |
| Total Displacement: 316 cu.in (5.18 L) |
| Rated Engine Power: 350 Hp (257.4 kW) at 3300 rpm |
| Fuel System Type: Direct injection |
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The Yanmar 6LYA-STE is a vertical, four-cycle,
inline six-cylinder marine diesel engine. This high-output powerplant
belongs to the 6LY family, sharing a displacement of 5.184 liters with
the UTE and STP variants, but tuned for a higher power rating that makes
it a preferred choice for fast cruisers and sportfishing boats. The
engine features direct injection, turbocharging, and a seawater-cooled
intercooler.
The Yanmar 6LYA-STE utilizes a mechanical in-line fuel injection pump
rather than an electronic common rail system, a design choice that
simplifies servicing in remote locations. The engine is known for its
narrow block configuration, which facilitates installation in tight
engine rooms or twin-engine setups in narrow hulls. Yanmar designed this
engine for planing hull applications where power-to-weight ratio is
critical. The 6LYA-STE is approved for use in both leisure and light
commercial vessels and has a documented history of reliability in
demanding marine environments.
The Yanmar 6LYA-STE is a four-cycle, water-cooled, inline six-cylinder
diesel engine with direct injection. The cylinder bore measures 100.0 mm
(3.94 in), while the piston stroke extends to 110.0 mm (4.33 in),
producing an oversquare configuration that favors power output at higher
engine speeds. Total displacement is 5,184 cc (5.184 L / 316 cu.in). The
compression ratio is 15.2:1 (effective compression ratio 14.0:1). The
firing order is 120° intervals: 1-2-3-4-5-6. Maximum output for the STE
variant is 257.4 kW (350 mhp / 350 hp) at 3,300 rpm.
The UTE variant produces 231.7 kW (315 hp) at the same engine speed.
Continuous rating is 213 kW (290 hp) at 3,100 rpm. Maximum torque
reaches 813 Nm (600 lb-ft) at 2,500 rpm. Maximum no-load speed is
3,720-3,725 rpm, with minimum no-load speed (low idle) set to 675-725
rpm. The direction of rotation, viewed from the stern (flywheel), is
counter-clockwise. The brake mean effective pressure at flywheel output
is 1.81 MPa (18.4 kgf/cm2).
The cylinder block is constructed from cast iron with a deep-skirt
design extending below the crankshaft centerline to maximize rigidity
under high cylinder pressures. The block features a conventional
inline-six configuration with cylinders cast directly into the iron
matrix. The cylinder bore surface is hardened through a plateau honing
process.
The block incorporates seven main bearing bulkheads supporting the
crankshaft. An integral oil gallery is drilled along the right side of
the block. The water jacket surrounds the cylinders and extends upward
to the block deck. The crankcase design includes mounting feet
positioned for a narrow overall width of 708-721 mm, facilitating
installation in tight engine compartments.
The cylinder head is manufactured from cast iron, providing thermal
stability and resistance to warpage under the elevated cylinder
pressures produced by turbocharging. The head employs an overhead valve
(OHV) configuration with four valves per cylinder, for a total of
twenty-four valves. The valvetrain is actuated by a camshaft located
within the cylinder block, driving pushrods and rocker arms.
The cylinder head features pressed-in replaceable valve guides. Valve
seat inserts are induction-hardened for intake ports and made of
heat-resistant alloy for exhaust ports. The cylinder head gasket is a
multi-layer steel (MLS) design. The cylinder head is detailed in the
parts catalogue for this engine model.
The fuel system employs direct injection with a mechanical in-line type
injection pump. The injection pump is the YPES 6AL type, manufactured by
Yanmar, and is gear-driven from the camshaft. A mechanical governor is
integrated into the injection pump housing, controlling engine speed
under varying loads. Static injection timing is set to 13° before top
dead center (BTDC).
Injection pressure is set to 25.48 ± 0.98 MPa (260 ± 10 kgf/cm2 / 3,698
± 142 psi). Fuel injection nozzles are of the hole type, designated
YDLLA-PL, with five holes of 0.34 mm diameter at a spray angle of 140°.
A diaphragm-type fuel feed pump supplies fuel from the tank to the
injection pump. The fuel system includes a primary filter with a water
separator. The engine stop device is cable-actuated on the mechanical
governor.
The lubrication system is a fully pressurized, wet-sump design using
forced lubrication with a gear-type pump. The oil pump is mounted inside
the oil pan and driven by the crankshaft. Oil pressure is regulated to
maintain adequate flow at all operating speeds. A water-cooled oil
cooler is integrated into the system to maintain oil temperature under
sustained high-load operation.
A spin-on full-flow oil filter is mounted to the engine block. The
lubrication system includes oil nozzles for piston cooling, directed at
the underside of each piston crown. Total lubricating oil capacity is
approximately 19.0-22.0 L depending on the oil pan configuration and
filter.
The cooling system is a pressurized, freshwater (closed) cooling design
with a belt-driven centrifugal fresh water pump. The pump circulates
coolant through the cylinder block, cylinder head, and a plate fin type
air cooler. A seawater pump, utilizing a rubber-impeller design, draws
seawater through a strainer and circulates it through the heat
exchanger, oil cooler, and exhaust mixing elbow.
The air cooler is of the seawater-cooled plate fin type with a single
pass on the seawater side and two passes on the air side. Fresh water
coolant capacity is 14.0-16.0 L depending on the heat exchanger
configuration. A wax-pellet thermostat, rated at 76-82°C (169-180°F),
controls coolant flow. The seawater pump impeller requires inspection
every 200 hours. The turbocharger is water-cooled through the engine's
fresh water circuit.
| Intake and Exhaust Systems |
Air Intake System: The air intake system is turbocharged with a
seawater-cooled intercooler. The turbocharger is an IHI RHC7W model, a
water-cooled unit with a turbine housing A/R ratio of 22. Boost pressure
ranges from 15 to 22 psi (103 to 152 kPa) depending on load. The air
cleaner is a dry-type paper element unit mounted to the turbocharger
inlet.
Exhaust System: The exhaust manifold is a single-piece, cast iron
water-cooled design. Seawater is injected into the exhaust mixing elbow
after the turbocharger to cool exhaust gases and reduce noise. The
exhaust elbow material is listed as a mixing elbow in the parts
catalogue.
The electrical system operates at 12 volts. The starter motor is a
gear-reduction type with a power rating of 2.5 kW (3.4 hp). The
alternator is a brushless, internally regulated unit rated at 80
amperes. Glow plugs are installed in each cylinder for cold start
assistance.
The complete engine dry weight without marine gear is 574-612 kg
(1,266-1,350 lb) depending on the transmission configuration. Overall
engine length ranges from 1,013 mm (39.9 in) for clutchless versions to
1,316 mm (51.8 in) for versions with marine gear. Maximum width is
707-721 mm (27.8-28.4 in), and height is 709-774 mm (27.9-30.5 in)
depending on the flywheel housing and mounting configuration. The
flywheel measures 392 mm (15.4 in) in diameter with a thickness of 65.9
mm (2.59 in).
Engine oil and oil filter change intervals are recommended every 250
operating hours or annually. The seawater pump impeller requires
inspection every 200 hours and replacement every 500 hours. Fuel filter
replacement occurs every 250 hours. The air cleaner element is inspected
every 250 hours.
Valve lash inspection and adjustment are performed every 500 hours.
Coolant replacement is required every 1,000 hours or 24 months. Zinc
anodes in the heat exchanger and intercooler require inspection every
200 hours and replacement when 50 percent consumed. The turbocharger
bearing clearance is checked every 1,500 hours.
Cylinder Head Bolts, Stage 1: 40 Nm (30 lb-ft)
Cylinder Head Bolts, Stage 2: 130 Nm (96 lb-ft)
Connecting Rod Cap Bolts: 80 Nm (59 lb-ft)
Main Bearing Cap Bolts: 200 Nm (148 lb-ft)
Flywheel Bolts: 120 Nm (89 lb-ft)
Camshaft Bearing Cap Bolts: 25 Nm (18 lb-ft)
Rocker Arm Shaft Bolts: 30 Nm (22 lb-ft)
Intake Manifold Nuts: 25 Nm (18 lb-ft)
Exhaust Manifold Nuts: 50 Nm (37 lb-ft)
Injector Clamp Bolts: 35 Nm (26 lb-ft)
Glow Plugs: 20 Nm (15 lb-ft)
Oil Pan Bolts: 15 Nm (11 lb-ft)
Water Pump Bolts: 20 Nm (15 lb-ft)
Crankshaft Pulley Bolt: 450 Nm (332 lb-ft)
Injection Pump Drive Gear Nut: 60 Nm (44 lb-ft)
Turbocharger Mounting Nuts: 50 Nm (37 lb-ft)
The Yanmar 6LYA-STE engine was utilized across multiple marine
platforms.
Sportfishing Boats: Primary propulsion for offshore sportfishing vessels
requiring high speed and reliability.
Fast Cruisers: Power for planing hull cruisers and motor yachts up to
40-45 ft length.
Downeast Boats: Installed in downeast-style vessels including the Little
Harbor Whisperjet 38.
Twin-Engine Configurations: Frequently installed in pairs for vessels
requiring redundancy and maneuverability.
Light Commercial Vessels: Workboats, pilot boats, and coastal patrol
craft.0
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