Yanmar 6LYA STP Specifications
| Engine Model: Yanmar 6LYA STP |
| Engine Type: 4-stroke inline 6-cylinder turbocharged water-cooled diesel |
| Total Displacement: 316 cu.in (5.18 L) |
| Rated Engine Power: 370 Hp (272 kW) at 3300 rpm |
| Fuel System Type: Direct injection |
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The Yanmar 6LYA-STP is a 6-cylinder,
turbocharged and intercooled marine diesel engine from the 6LYA series,
widely utilized in mid-sized vessels including trawlers, sportfishing
boats, and express cruisers. The engine is specifically noted for its
compact, narrow profile, which makes it a popular choice for repowering
projects where engine room space is constrained.
The Yanmar 6LYA-STP employs a direct injection combustion system, a
forged steel crankshaft, and a cast iron cylinder block with replaceable
dry liners. Fresh water cooling with a heat exchanger isolates the
engine block from seawater, while a belt-driven seawater pump with a
rubber impeller provides raw water for the intercooler, oil cooler, and
exhaust mixing elbow.
The engine meets EPA Tier 2 emission standards for commercial and
recreational marine applications. A notable production update occurred
at serial number M56928, where Yanmar introduced improved Inconel
exhaust valves for enhanced high-temperature durability. Vessels using
this engine include the Beneteau Swift Trawler 42, often in twin-engine
installations, paired with ZF 80-A marine gears.
The Yanmar 6LYA-STP is a vertical, inline 6-cylinder, 4-stroke,
water-cooled, turbocharged and intercooled diesel engine. The inline
6-cylinder configuration provides inherent primary and secondary
balance, eliminating the need for a balance shaft and contributing to
smooth operation across the engine speed range.
Engine Type: Vertical, inline 6-cylinder, 4-stroke, turbocharged and
intercooled diesel.
Displacement: 5.184 L (316 cu.in).
Bore x Stroke: 100 mm x 110 mm (3.94 in x 4.33 in).
Combustion System: Direct injection.
Aspiration: Turbocharged with seawater-cooled intercooler (charge air
cooler).
Maximum Output (Crankshaft): 272 kW (370 hp) at 3300 rpm.
Continuous Output (Crankshaft): 213 kW (290 hp) at 3100 rpm.
Maximum Torque: 840 Nm (620 lb-ft) at 2200 rpm.
Firing Order: 1-5-3-6-2-4.
Compression Ratio: 16.5:1.
Idling Speed: 650 to 750 rpm (in neutral).
Rotation (Crankshaft): Counterclockwise as viewed from the stern
(flywheel end).
Fuel Consumption (maximum output): 68 L/hr (18.0 US gal/hr).
Fuel Consumption (continuous output): 54 L/hr (14.3 US gal/hr).
The cylinder block is constructed from high-strength cast iron with a
deep-skirt design that extends below the crankshaft centerline,
providing increased structural rigidity for the main bearing bulkheads.
The block houses seven main bearing supports for the forged steel
crankshaft. Replaceable dry-type cylinder liners are pressed into the
parent block material.
Each liner is made of centrifugally cast alloy iron with a hardened
internal bore surface finished with a plateau hone. The dry liner design
eliminates coolant contact with the liner exterior, reducing cavitation
erosion risks compared to wet liner engines. The block incorporates a
front-mounted gear train housing that drives the camshaft, injection
pump, and auxiliary drives. A structural oil pan, fabricated from
pressed steel, bolts to the lower flange of the block.
The cylinder head is a single-piece, cast-iron cross-flow unit covering
all six cylinders. The overhead valve (OHV) configuration places the
camshaft within the cylinder block. Pushrods and rocker arms actuate the
valves. Four valves per cylinder (two intake, two exhaust) produce a
total of 24 valves. The 4-valve arrangement improves volumetric
efficiency and allows central placement of the fuel injector for optimum
spray symmetry within the piston combustion bowl.
The intake ports are designed as high-swirl passages to promote air-fuel
mixing. The valvetrain uses mechanical lash adjusters (screw and locknut
type). Valve Clearance (cold engine): Intake: 0.25 mm (0.010 in).
Exhaust: 0.35 mm (0.014 in). For engines with serial number M56928 and
later, exhaust valves are manufactured from Inconel, a nickel-chromium
superalloy resistant to high-temperature corrosion and fatigue. Earlier
engines (serial number M56927 and lower) used a different valve material
and require additional attention during high-load operation.
The fuel system is a mechanical direct injection design. An in-line
injection pump (Bosch P-type or Yanmar licensed equivalent) is mounted
on the side of the cylinder block and driven by the engine gear train.
The pump features one plunger and barrel assembly per cylinder arranged
in line. A mechanical centrifugal governor integrated into the pump
housing regulates engine speed by controlling the fuel rack position.
An electric stop solenoid provides remote shutdown capability. A
gear-type transfer pump draws fuel from the tank through a primary fuel
filter with a water separator. High-pressure steel injection lines route
fuel to six mechanical injectors, one per cylinder. Each injector opens
at a calibrated crack pressure, atomizing fuel directly into the
re-entrant combustion bowl machined into the piston crown.
Fuel Injection Timing: 8° BTDC (standard calibration).
Injector Opening Pressure: 24.5 MPa (3550 psi).
The lubrication system is a fully pressurized, forced-feed circuit
designed for sustained high-load marine operation. A rotor-type
(trochoid) oil pump, driven from the front of the crankshaft, draws oil
through a strainer from a pressed steel sump. Oil passes through a
full-flow spin-on canister filter mounted on the side of the block.
A seawater-cooled oil cooler, integrated into the system, maintains oil
temperature under high load conditions such as continuous cruising at
3100 rpm. A pressure regulating valve maintains system pressure. Piston
cooling jets are installed, directing a continuous stream of oil at the
underside of each piston crown to manage combustion temperatures.
Total Oil Capacity (with filter): 14.5 L (15.3 qt).
Recommended Oil Grade: SAE 15W-40 meeting API CI-4 or higher
specification.
Oil Pressure (rated speed, warm engine): 350 to 450 kPa (51 to 65 psi).
Oil Pressure (idle, warm engine): Minimum 98 kPa (14 psi).
The 6LYA-STP employs an indirect fresh water cooling system with a heat
exchanger. A belt-driven centrifugal fresh water pump circulates coolant
through the cylinder block, cylinder head, and a shell-and-tube or
plate-type heat exchanger. Within the heat exchanger, raw seawater
pumped by a separate belt-driven flexible-impeller pump (mounted on the
front of the engine) absorbs heat from the freshwater circuit.
Seawater then passes through the intercooler (charge air cooler), the
oil cooler, and finally exits through the exhaust mixing elbow. A
thermostatically controlled bypass circuit permits coolant circulation
within the engine during warm-up. An expansion tank with a pressure cap
is integrated into the fresh water circuit.
Freshwater Coolant Capacity (engine and heat exchanger): 12.0 L (12.7
qt).
Seawater Pump Type: Rubber impeller, flexible vane pump.
Intercooler Type: Seawater-cooled, tube-and-fin configuration mounted on
the engine or remotely.
Thermostat Start Opening Temperature: 76°C (169°F).
Thermostat Fully Open Temperature: 88°C (190°F).
| Intake and Exhaust Systems |
Air Intake System: A dry-type paper air cleaner element mounted on the
turbocharger compressor inlet. Optional flame arrestor for inboard
engine rooms.
Exhaust System: A water-cooled mixing elbow bolted to the turbocharger
outlet. Seawater from the heat exchanger is injected into the elbow to
cool exhaust gases before they pass through a flexible hose to a
waterlock muffler and overboard outlet.
Electrical System: 12-volt negative ground. A gear-reduction starter
motor rated at 2.5 kW is standard. A 12V - 80A alternator (Hitachi or
equivalent) is standard equipment.
Control System: A mechanical cable-actuated remote control system
operates the fuel injection pump throttle and the marine gear clutch
(forward/neutral/reverse). Electronic controls are available as an
option on later production models.
Turbocharger: A fixed geometry or wastegate turbocharger (IHI or
Mitsubishi) provides boost pressure up to approximately 1.5 bar (22
psi). The turbocharger is mounted on a single-entry exhaust manifold.
Intercooler (Charge Air Cooler): A seawater-cooled air-to-water
intercooler mounted on the engine or remotely. The intercooler reduces
intake air temperature from approximately 150°C (302°F) to 50°C (122°F),
increasing charge density and combustion efficiency.
Cold Start Aid: An intake air heater (glow plug type) or thermostart
flame-type heater is available as an option for cold climates below 10°C
(50°F).
Engine Mounts: Four flexible rubber mounts are standard. The engine is
rated for a maximum continuous inclination of 15° in the longitudinal
axis and 25° in the transverse axis for temporary operation.
Dry Weight (bobtail, without gearbox or heat exchanger): 510 kg (1124
lb).
Weight with ZF 80-A Marine Gear: 590 kg (1300 lb).
Overall Length (bobtail, front pulley to flywheel housing): 1210 mm
(47.6 in).
Overall Length (with ZF 80-A gear): 1450 mm (57.1 in).
Overall Width (exhaust manifold outer to starter motor outer): 780 mm
(30.7 in).
Overall Height (oil pan bottom to rocker cover top): 875 mm (34.4 in).
Crankshaft Centerline Height (from bottom of oil pan rail): 300 mm (11.8
in).
Oil Change Interval: 200 hours or annually, whichever occurs first. For
commercial duty (continuous operation above 80% load), reduce to 100
hours. Oil Filter Replacement: At every oil change. Use Yanmar genuine
filter element or an approved equivalent (Fleetguard, Baldwin). Fuel
Filter Replacement (primary with water separator): 200 hours or
annually. Drain water separator weekly. Fuel Filter Replacement
(secondary): 400 hours or every second oil change.
Valve Clearance Inspection: 500 hours. Injector Service Interval: Test
spray pattern and crack pressure at 1000 hours. Replace nozzle tips at
2000 hours. Timing Gear Train: The 6LYA series uses a gear train for
camshaft drive (no chains or belts). No replacement interval is
specified. Inspect gear backlash at major overhaul (4000 hours). Drive
Belt (alternator/freshwater pump): Inspect at 200 hours. Replace at 400
hours or earlier if cracks or glazing are visible.
Coolant Replacement: 1000 hours or 2 years. Use ethylene glycol
antifreeze with supplemental coolant additive (SCA). Seawater Pump
Impeller Replacement: 200 hours or annually. Inspect at each oil change
for cracked or missing vanes. Heat exchanger (Freshwater Cooler):
Inspect and clean sacrificial zinc anodes at 200 hours; replace when
consumed by more than 50%. Clean tube stack at 1000 hours. Intercooler
(Charge Air Cooler): Inspect seawater side for fouling at 400 hours.
Clean with descaler solution if necessary.
Engine Mount Inspection: Inspect for rubber deterioration and fluid
leakage at 500 hours. Turbocharger Inspection: Visual check of shaft
axial play at 1000 hours. Replace if end play exceeds 0.3 mm (0.012 in).
Check turbine wheel for erosion or contact marks. Exhaust Elbow
Inspection: Inspect for internal corrosion and water leakage at 500
hours. Replace every 2000 hours in seawater-cooled configurations.
Cylinder Head Bolts (M14), Stage 1: 60 Nm (44 lb-ft).
Cylinder Head Bolts (M14), Stage 2: 140 Nm (103 lb-ft).
Connecting Rod Bolts (M12 x 1.25): 44 Nm (32 lb-ft).
Main Bearing Cap Bolts (M14), Stage 1: 100 Nm (74 lb-ft)..
Main Bearing Cap Bolts (M14), Stage 2: 140 Nm (103 lb-ft).
Main Bearing Cap Side Bolts (M10, cross bolts): 50 Nm (37 lb-ft).
Flywheel Bolts (to crankshaft flange, M12): 90 Nm (66 lb-ft).
Flywheel Housing Bolts (to block, M12): 90 Nm (66 lb-ft).
Crankshaft Damper Pulley Bolt (center, M20): 100 Nm (74 lb-ft).
Camshaft Thrust Plate Bolts (M8): 26 Nm (19 lb-ft).
Rocker Arm Shaft Bracket Bolts (M10): 50 Nm (37 lb-ft).
Rocker Arm Adjusting Locknut (M8): 16 Nm (12 lb-ft).
Valve Cover Nuts (M6): 11 Nm (8 lb-ft).
Injector Hold-Down Clamp Bolts (M8): 26 Nm (19 lb-ft).
Injection Pump Mounting Nuts (M10): 50 Nm (37 lb-ft).
Injection Pump Drive Gear Bolt (M12): 90 Nm (66 lb-ft).
High-Pressure Fuel Line Nuts (M14): 30 Nm (22 lb-ft).
Injection Nozzle Holder Assembly (to cylinder head, M14): 70 Nm (52
lb-ft).
Oil Pump Mounting Bolts (M8): 21 Nm (15 lb-ft).
Oil Cooler Mounting Bolts (M10): 40 Nm (30 lb-ft).
Water Pump Mounting Bolts (fresh water, M8): 21 Nm (15 lb-ft).
Seawater Pump Mounting Bolts (M8, aluminum housing): 15 Nm (11 lb-ft).
Thermostat Housing Bolts (M8, aluminum): 15 Nm (11 lb-ft).
Starter Motor Mounting Bolts (M12): 70 Nm (52 lb-ft).
Alternator Pivot Bolt (M10): 40 Nm (30 lb-ft).
Turbocharger Mounting Nuts (M10): 40 Nm (30 lb-ft).
Turbocharger Oil Drain Line (to block, M10): 35 Nm (26 lb-ft).
Intercooler Mounting Bolts (to block, M10 aluminum casting): 30 Nm (22
lb-ft).
Exhaust Manifold Nuts (M10): 50 Nm (37 lb-ft).
Exhaust Elbow Bolts (to turbocharger, M10): 40 Nm (30 lb-ft).
Engine Mount Bracket Bolts (to block, M12): 90 Nm (66 lb-ft).
Marine Gear Adapter Bolts (flywheel housing to gearbox, M12): 90 Nm (66
lb-ft).
The Yanmar 6LYA-STP is used exclusively in marine applications, serving
as both a single-engine installation and twin-engine installation for
vessels up to 60 feet (18 meters) in length.
Trawlers:
Beneteau Swift Trawler 42 (twin 6LYA-STP engines; standard or optional
power).
Beneteau Swift Trawler 44 (twin engines).
Grand Banks 42 Heritage (repower application).
American Tug 34 (single engine).
Nordic Tug 32, 37 (repower).
Sportfishing Boats (Convertible and
Express):
Pursuit S378, S408, S428 (twin engines).
Grady-White Canyon 376, 456 (twin engines).
Regulator 34 FS, 41 FS (twin engines).
Contender 39 ST, 44 ST (twin or triple engines).
Yellowfin 42 (twin engines).
Viking 48 Convertible (repower application).
Express Cruisers and Downeast Boats:
Hinckley 36 Picnic Boat (single engine).
Sabre 42 Express (twin engines).
MJM 40 Z (twin engines).
Back Cove 37, 41 (single or twin engines).
Commercial Vessels:
Pilot boats up to 15 meters (49 feet).
Small passenger ferries (capacity up to 40 persons).
Patrol boats for police, customs, and coast guard agencies.
Small fishing vessels (purpose-built or repowered).
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