Yanmar 4LHA DTE Specifications
| Engine Model: Yanmar 4LHA DTE |
| Engine Type: 4-stroke inline 4-cylinder turbocharged water-cooled diesel |
| Total Displacement: 210.9 cu.in (3.45 L) |
| Rated Engine Power: 170 Hp (125 kW) at 3300 rpm |
| Fuel System Type: Direct injection |
____________________________________________________________________________________
The Yanmar 4LHA DTE is a compact, high-speed
marine diesel engine that represents a specific power rating within the
renowned LHA series. Configured as a 4-stroke, vertical, water-cooled
in-line four-cylinder, this engine delivers 170 horsepower, positioning
it as an intermediate option between lower-output recreational engines
and the higher-output 4LHA-DTP variant that succeeded it. The DTE
designation signifies Direct Injection, Turbocharged, and the inclusion
of a seawater-intercooled charge air cooler.
Marine operators value the 4LHA DTE for its favorable power-to-weight
ratio, compact installation envelope, and the inherent durability of
Yanmar’s indirect and direct injection lineage. The engine incorporates
a rubber-type flexible mounting system to mitigate harmonic vibration, a
critical feature for planing hull vessels operating across varying rpm
ranges. While later electronic and common-rail designs have superseded
this mechanically governed engine in production, the 4LHA DTE remains
operational in countless fishing boats, cruisers, and light commercial
craft, prized for its straightforward service access and predictable
mechanical fuel control.
The Yanmar 4LHA DTE operates on the four-stroke diesel cycle, completing
intake, compression, power, and exhaust strokes over two crankshaft
revolutions. Its vertical in-line configuration provides natural primary
and secondary balance, aided by a harmonic damper on the front of the
crankshaft. The engine employs a direct injection combustion system,
where fuel is injected directly into the cylinder bowl-in-piston design,
rather than into a pre-combustion chamber. This approach yields lower
specific fuel consumption and easier cold starting compared to indirect
injection designs.
Engine Type: 4-stroke, vertical, in-line 4-cylinder, turbocharged
diesel.
Total Displacement: 3.455 L (210.9 cu.in)
Bore: 100 mm (3.94 in)
Stroke: 110 mm (4.33 in)
Compression Ratio: 16.5:1 to 17.5:1.
Maximum Output: 170 hp (125 kW) at 3,300 rpm
Continuous Rating (Marine Duty): 154 hp (113.3 kW) at 3,200 rpm.
Peak Torque: 280-320 lb-ft (380-434 Nm) at 2,000-2,200 rpm.
Firing Order: 1-3-4-2.
Direction of Rotation: Counter-clockwise when viewed from the stern.
Aspiration: Turbocharged with a seawater-cooled intercooler. The
turbocharger compresses intake air, and the intercooler reduces air
temperature before entry into the cylinder head, increasing charge
density and combustion efficiency.
The cylinder block is a single, rigid cast-iron component incorporating
the four cylinder bores machined directly into the block. Unlike
wet-liner designs, the 4LHA DTE uses a parent bore (no removable
liners), which simplifies manufacturing and reduces the number of
sealing interfaces. The block features a deep-skirt design extending
below the crankshaft centerline, providing substantial support for the
main bearing caps.
Internal oil galleries are cast into the block to supply pressurized
lubricant to the main bearings, connecting rods, and the cylinder head.
Cooling passages circulate fresh water around each cylinder bore and
into the cylinder head. The block is also fitted with mounting bosses
for the flexible rubber engine mounts, which are specified for this
series to reduce transmission of vibration into the hull structure. An
access port on the starboard or port side provides inspection capability
for the timing gears and front gear train.
The cylinder head is a single cross-flow cast-iron component that spans
all four cylinders. The cross-flow design means intake air enters from
one side of the head (connected to the intercooler and turbocharger) and
exhaust gases exit from the opposite side, reducing thermal loading on
the head. Each cylinder is served by two intake valves and two exhaust
valves (four valves per cylinder), a configuration that improves
volumetric efficiency and permits better breathing at higher engine
speeds.
The valves are actuated by a single overhead camshaft (OHC) via bucket
tappets or roller rocker arms, depending on the specific production
variant. The direct injection combustion chamber is machined into the
cylinder head’s fire deck, with the injector positioned centrally to
deliver fuel into the piston bowl. Valve clearances require periodic
inspection and adjustment, specified later in the maintenance section.
The cylinder head is secured to the block using high-strength bolts or
studs with a defined tightening sequence to ensure even clamping force
across the cylinder head gasket.
The 4LHA DTE employs a mechanical direct injection fuel system,
characteristic of Yanmar marine engines of this era. A mechanical
in-line injection pump, mounted on the engine block and driven by the
timing gear train, pressurizes fuel and delivers it to each cylinder at
precisely timed intervals. The pump incorporates a mechanical governor
that controls engine speed by varying the quantity of fuel injected per
cycle. The governor responds to throttle lever position and engine load,
maintaining set rpm under varying sea conditions.
From the injection pump, high-pressure fuel lines carry fuel to the
multi-hole nozzle injectors, which are screwed into the cylinder head.
Injector opening pressure is preset and requires calibration on a test
bench during overhaul. A hand priming lever on the feed pump aids in
bleeding air from the system after filter changes. The fuel system does
not incorporate electronic controls or common-rail technology;
mechanical reliability and field serviceability define this design.
The lubrication system is a forced-feed, full-pressure design. A
gear-type lubrication pump, driven directly from the crankshaft, draws
oil from a sump located at the bottom of the engine. The pump pushes oil
through a full-flow spin-on cartridge oil filter and an oil cooler
before distributing it to the main oil gallery. The oil cooler uses
engine coolant (fresh water) as the cooling medium, which stabilizes oil
temperature across varying engine loads.
From the main gallery, oil is routed to the crankshaft main bearings,
connecting rod bearings, camshaft bearings, valve train components, and
the turbocharger center housing. A piston cooling jet may be present on
some variants, directing a stream of oil to the underside of the piston
crown. The lubrication system also supplies the rubber impeller seawater
pump bearings, though this pump is not lubricated by engine oil. The oil
sump capacity is designed to accommodate the severe pitching and rolling
encountered in marine applications.
Normal Oil Pressure: 40-60 psi (276-414 kPa) at operating rpm; minimum
10 psi (69 kPa) at hot idle. Oil Capacity: Not specified in source;
reference 4LHA series suggests 8-10 quarts (7.6-9.5 L) including filter.
Oil Specification: API class CD or higher is specified for this series.
Modern equivalents include API CI-4, CJ-4, or CK-4 in appropriate
viscosity grade (SAE 15W-40 recommended for most temperate marine
conditions).
The cooling system is a dual-circuit, fresh water and seawater
arrangement, known as indirect cooling. The primary circuit uses fresh
water with corrosion inhibitors as the coolant. A centrifugal fresh
water pump circulates coolant through the cylinder block, cylinder head,
oil cooler, and then through a seawater-cooled heat exchanger.
The heat exchanger functions as a radiator; seawater from the secondary
circuit passes through tubes within the heat exchanger, absorbing heat
from the fresh water without mixing. The secondary circuit employs a
rubber impeller seawater pump, which draws raw water through a hull
strainer and seacock. After passing through the heat exchanger, the
seawater cools the turbocharger’s charge air cooler (intercooler) and
then exits through the exhaust elbow, mixing with exhaust gases before
discharge overboard.
A thermostat regulates fresh water temperature by bypassing the heat
exchanger until operating temperature is reached. Coolant Temperature:
160°F-185°F (71°C-85°C) under normal load, regulated by a thermostat.
Coolant Capacity: 6-8 quarts (5.7-7.6 L) for engine side excluding heat
exchanger.
Electrical System: 12V DC with a 2.5 kW electric starter motor. The
charging system uses a 12V 55A AC alternator. The alternator is
belt-driven from the crankshaft pulley and includes an internal voltage
regulator. A start-stop panel with audible alarms for low oil pressure
and high coolant temperature is standard for marine installation.
Air Induction System: Air enters through a flame arrestor or intake
silencer, then passes through the turbocharger compressor housing.
Compressed air travels to the seawater-cooled intercooler, which reduces
intake air temperature from approximately 300°F-350°F (150°C-175°C) down
to 100°F-120°F (38°C-49°C). The cooled, dense air then enters the
cylinder head intake ports.
Exhaust System: A water-cooled exhaust manifold and turbocharger casing
direct exhaust gases into a mixing elbow. Seawater injected into the
elbow cools the exhaust and reduces noise before expulsion through a
rubber hose and overboard fitting.
Mounting System: Rubber-type flexible mounts are specified for this
engine. Four mounts attach to the engine’s lifting brackets and cylinder
block, then bolt to hull stringers. This mounting method reduces
harmonic vibration transmission.
Length: 41.7 in (1,060 mm) from front pulley to flywheel housing.
Width: 26.5 in (675 mm) across cylinder head and heat exchanger.
Height: 28.5 in (725 mm) from oil pan to top of turbocharger.
Dry Weight: 380 kg (839 lbs) without marine gear. With a standard
hydraulic marine transmission, weight increases by 50-65 kg (110-143
lbs).
Oil Change Interval: 200-250 operating hours or annually, whichever
occurs first. Severe duty (heavy loads, frequent maneuvering) requires
100-150 hour intervals. Oil Filter Change: Replace with every oil
change. Use a genuine Yanmar or equivalent high-quality full-flow
filter. Injector Service: Remove, test, and calibrate injectors every
1,000-1,500 hours. Replace nozzle tips if spray pattern is degraded.
Fuel Filter Change: Primary (water-separating) filter replaced at
250-400 hours. Secondary spin-on filter replaced every 400 hours or
sooner if fuel contamination is suspected. Valve Clearance Inspection:
Every 500-800 operating hours. Cold valve clearances (intake and
exhaust) are set to 0.008-0.010 in (0.20-0.25 mm) for most 4LHA
variants. Seawater Pump Impeller Replacement: Inspect annually and
replace every 500-800 hours or at first sign of cracking or vane
separation. Carry a spare impeller on board.
Thermostat Check: Remove, inspect, and test thermostat opening
temperature every 1,000 hours. Intercooler Service: Remove, disassemble,
and clean seawater passages every 1,000-1,500 hours to prevent fouling
and overheating. Turbocharger Inspection: Check for shaft end-play and
radial clearance every 1,000 hours. Clean compressor housing if oil or
debris is observed.
Cylinder Head Bolts, Step 1: 25-30 lb-ft (34-41 Nm).
Cylinder Head Bolts, Step 2: 60-65 lb-ft (81-88 Nm).
Connecting Rod Bolts: 35-40 lb-ft (47-54 Nm).
Main Bearing Cap Bolts: 65-75 lb-ft (88-102 Nm).
Flywheel Bolts: 50-55 lb-ft (68-75 Nm).
Injection Pump Mounting Nuts: 15-18 lb-ft (20-24 Nm).
Injector Clamp Bolts: 18-20 lb-ft (24-27 Nm).
Rocker Arm Shaft Bracket Bolts: 25-28 lb-ft (34-38 Nm).
Valve Cover Nuts: 7-9 lb-ft (9-12 Nm).
Exhaust Manifold Nuts: 25-30 lb-ft (34-41 Nm).
Heat Exchanger End Cover Bolts: 6-8 lb-ft (8-11 Nm).
The Yanmar 4LHA DTE is exclusively a marine propulsion engine.
Recreational Powerboats: Deep-V hulls, semi-displacement cruisers, and
planing fishing boats (25-35 ft / 7.6-10.7 m) where speeds of 25-35
knots are desired.
Light Commercial Vessels: Patrol boats, pilot boats, small crew transfer
vessels, and dive boats requiring reliable high-speed operation.
Sportfishing Yachts: As a single or twin installation, often paired with
a ZF or Hurth marine transmission to power propeller shafts or stern
drives.
Pleasure Trawlers: In semi-displacement hulls where the 170 hp rating
provides a cruise speed of 12-18 knots and a hull-speed maximum near 20
knots.
Rigid Inflatable Boats (RIBs): Large RIBs from 30-38 ft (9-11.5 m)
operated by coast guards, navies, and rescue services, where the
engine’s favorable power-to-weight ratio supports high-speed intercept
missions.
____________________________________________________________________________________
| Industrial Engines Technical Specifications |
| Car Engines Technical Specifications |
| Small Engines Technical Specifications |
| Outboard Engines Technical Specifications |
