Yanmar 3JH30A Specifications
| Engine Model: Yanmar 3JH30A |
| Engine Type: 4-stroke inline 3-cylinder naturally aspirated water-cooled diesel |
| Total Displacement: 83.2 cu.in (1.36 L) |
| Rated Engine Power: 32.6 Hp (24.3 kW) at 3000 rpm |
| Fuel System Type: Direct injection |
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The Yanmar 3JH30A is a vertical, four-cycle,
three-cylinder marine diesel engine produced by Yanmar Co., Ltd. This
powerplant gained recognition for its use as a prime mover in lifeboats,
including free-fall lifeboat systems, where its robust design and
ability to withstand severe impact forces are critical. The 3JH30A is a
member of the JH Series propulsion engines, a family of high-speed
marine diesels engineered for compact vessels including sailboats, small
fishing craft, workboats, and pleasure boats. The engine design
emphasizes reduced weight and compact dimensions without sacrificing
durability, making it suitable for installations where space is limited.
The Yanmar 3JH30A employs direct injection combustion, a naturally
aspirated induction system, and freshwater cooling with a heat exchanger
or keel cooling option. Yanmar produced this engine in multiple
variants, including the base 3JH30A and the 3JH30A-K with different
transmission configurations. The engine meets the stringent requirements
for lifeboat applications, including the ability to start and operate
reliably after a free-fall launch. It remains supported through Yanmar's
global parts and service network.
The Yanmar 3JH30A is a four-cycle, water-cooled, inline three-cylinder
diesel engine with direct injection. The cylinder bore measures 82.0 mm
(3.23 in), while the piston stroke extends to 86.0 mm (3.39 in),
creating a slightly undersquare configuration that favors torque
production in the mid-range. Total displacement is 1,363 cc (1.363 L /
83.2 cu.in). The compression ratio is 18.5:1 to 19.5:1. The firing order
is 1-3-2-1, a non-standard sequence reflecting the three-cylinder
configuration. Continuous rated output is 22.1 kW (29.6 hp) at 2,900
rpm.
Maximum output reaches 24.3 kW (32.6 hp) at 3,000 rpm. Peak torque is
estimated at 80-85 Nm (59-63 lb-ft) at 2,200-2,400 rpm. Low idle speed
is set to 650-700 rpm, with governed high idle of 3,000 rpm. The
direction of rotation, viewed from the stern, is counter-clockwise at
the crankshaft, producing clockwise rotation at the propeller shaft
through the reduction gear. Compression pressure at cranking speed is
0.539-0.670 MPa (78-97 psi) depending on the specific variant.
The cylinder block is constructed from cast iron, a material selected
for its strength, wear resistance, and dimensional stability under the
vibration and thermal cycling characteristic of marine diesel operation.
The block features a conventional inline-three configuration with
cylinders cast directly into the iron matrix. The cylinder bore surface
is hardened through a plateau honing process. The block incorporates
four main bearing bulkheads supporting the crankshaft.
An oil gallery is drilled along the right side of the block to supply
pressurized oil to the main bearings, camshaft bearings, and rocker arm
assembly. The water jacket surrounds the cylinders and extends upward to
the block deck. A cast iron oil pan forms the lower crankcase enclosure.
The engine number is stamped on a machined pad located on the right side
of the block. Freeze plugs are pressed into the block at three
locations.
The cylinder head is manufactured from cast iron, providing thermal
stability and resistance to warpage under sustained marine operation.
The head employs an overhead valve (OHV) configuration with two valves
per cylinder, for a total of six valves. The valvetrain is actuated by a
camshaft located within the cylinder block, driving pushrods and rocker
arms.
The intake valve head diameter measures 36.0 mm (1.42 in), while the
exhaust valve diameter is 32.0 mm (1.26 in). Valve stems are 7.0 mm
(0.276 in) in diameter and are chrome-plated for wear resistance. 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.
Valve lash is adjusted with the engine cold. Intake valve clearance is
set to 0.20 mm (0.008 in), and exhaust valve clearance is set to 0.25 mm
(0.010 in). The cylinder head gasket is a multi-layer steel (MLS)
design. Ten cylinder head bolts retain the head to the block. The
injector nozzles are of the hole type, located centrally in the
combustion chamber.
The fuel system employs direct injection with a Bosch-type in-line
mechanical injection pump mounted to the right side of the engine block.
The injection pump is gear-driven from the camshaft and incorporates a
mechanical flyweight governor to maintain engine speed under varying
loads. Injection pressure is set to 120-130 bar (1,740-1,885 psi). Each
cylinder is served by an individual injection line connecting the pump
to a nozzle holder assembly with a multi-hole nozzle. Injector opening
pressure is set to 115 bar (1,668 psi) for the 3JH30A.
A diaphragm-type transfer pump, integrated into the injection pump
housing, draws fuel from the tank through a primary filter with a water
separator. A secondary spin-on fuel filter of 5-micron rating is located
between the transfer pump and the injection pump. Static injection
timing is set to 8-10° BTDC, measured at the injection pump drive shaft.
A hand primer pump on the secondary filter head allows system priming
after filter replacement. The return system routes excess fuel from the
injection pump and injectors back to the fuel tank.
The lubrication system is a fully pressurized, wet-sump design using a
trochoid-type pump for forced lubrication. The oil pump is driven
directly by the crankshaft and is mounted inside the oil pan on the rear
main bearing cap. Oil pressure at rated engine speed (2,900 rpm) is
maintained between 30 and 50 psi (207 and 345 kPa). Total oil capacity,
including the oil filter, is 4.4 L (4.65 U.S. qt). A spin-on full-flow
oil filter is mounted to the engine block on the intake side.
The system incorporates a bypass valve that opens at 25 psi (172 kPa)
differential pressure if the filter becomes restricted. The oil pump
relief valve is set to 60 psi (414 kPa). The oil pan is constructed from
stamped steel with a capacity of 3.5 L (3.7 U.S. qt). A dipstick is
located on the right side of the block. Recommended oil viscosity is SAE
15W-40 or SAE 10W-30 meeting API CD or higher diesel rating. Piston
cooling relies on splash lubrication from the connecting rod oil
passages.
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 heat exchanger.
A seawater pump, utilizing a rubber-impeller design, draws seawater
through a strainer and circulates it through the heat exchanger to
remove heat from the fresh water circuit. Coolant capacity for the fresh
water side is 2.0 L (2.1 U.S. qt) for the engine alone. A wax-pellet
thermostat, rated at 76-82°C (169-180°F), controls coolant flow to the
heat exchanger.
A bypass circuit allows coolant circulation inside the engine when the
thermostat is closed. The expanion tank is integrated into the heat
exchanger or provided as a remote tank. An optional keel cooling
configuration replaces the heat exchanger with a keel-mounted cooling
coil. The seawater pump impeller requires inspection every 200 hours.
Coolant recommendations call for a 50/50 mixture of ethylene glycol
antifreeze and distilled water.
The electrical system operates at 12 volts. The starter motor is a
gear-reduction type with a solenoid-actuated pinion engaging the
flywheel ring gear. Starter motor power rating is 1.8 kW (2.4 hp). The
alternator is a brushless, internally regulated unit rated at 35
amperes. Glow plugs are installed in each cylinder for cold start
assistance, with an automatic controller managing pre-heat and post-heat
cycles.
Exhaust System: The exhaust manifold is a single-piece, cast iron
water-cooled design. Seawater is injected into the exhaust elbow after
the manifold to cool exhaust gases and reduce noise. The exhaust system
incorporates a waterlock to prevent seawater backflow into the engine.
Transmission Options: The 3JH30A is paired with Kanzaki mechanical cone
clutch transmissions. Forward reduction ratio is 2.36:1, and reverse
reduction ratio is 3.16:1.
The complete engine dry weight without transmission is 175-190 kg
(386-419 lb) depending on the specific variant and cooling
configuration. With the KMP35P1 marine gear installed, dry mass is 187
kg (412 lb). Overall engine length including transmission is 770 mm
(30.3 in). Maximum width, measured across the engine, is 545 mm (21.5
in). Height, from the oil pan rail to the top of the rocker arm cover,
is 680 mm (26.8 in). The flywheel housing conforms to Yanmar's
proprietary bolt pattern.
Engine oil and oil filter change intervals are recommended every 150
operating hours or annually, whichever occurs first. The seawater pump
impeller requires inspection every 200 hours and replacement every 500
hours. The timing belt is not present; the camshaft is gear-driven. Fuel
filter replacement occurs every 200 hours. Coolant requires testing
every 400 hours, with replacement every 2,000 hours or 24 months.
Valve lash inspection and adjustment are performed every 500 hours. The
air cleaner element is replaced every 400 hours. Zinc anodes in the heat
exchanger require inspection every 200 hours and replacement when 50
percent consumed. Injector service is required every 1,000 hours. The
water pump is inspected annually. Piston ring end gap for new rings is
0.25-0.35 mm (0.010-0.014 in) for compression rings and 0.30-0.45 mm
(0.012-0.018 in) for oil rings.
Cylinder Head Bolts, Stage 1: 25 Nm (18 lb-ft)
Cylinder Head Bolts, Stage 2: 60 Nm (44 lb-ft)
Connecting Rod Cap Bolts: 39 Nm (29 lb-ft)
Main Bearing Cap Bolts: 78 Nm (58 lb-ft)
Flywheel Bolts: 65 Nm (48 lb-ft)
Camshaft Bearing Cap Bolts: 20 Nm (15 lb-ft)
Rocker Arm Shaft Bolts: 22 Nm (16 lb-ft)
Intake Manifold Nuts: 20 Nm (15 lb-ft)
Exhaust Manifold Nuts: 25 Nm (18 lb-ft)
Injector Clamp Bolts: 25 Nm (18 lb-ft)
Glow Plugs: 15 Nm (11 lb-ft)
Oil Pan Bolts: 12 Nm (9 lb-ft)
Water Pump Bolts: 12 Nm (9 lb-ft)
Crankshaft Pulley Bolt: 120 Nm (89 lb-ft)
Injection Pump Drive Gear Nut: 40 Nm (30 lb-ft)
Starter Motor Bolts: 45 Nm (33 lb-ft)
Alternator Mounting Bolts: 25 Nm (18 lb-ft)
The Yanmar 3JH30A engine was utilized
across multiple marine platforms:
Lifeboats: Primary prime mover for free-fall and davit-launched lifeboat
systems.
Sailboats: Auxiliary propulsion for yachts and cruising sailboats up to
40 ft length.
Small Fishing Vessels: Primary propulsion for inshore and coastal
fishing craft.
Workboats: Propulsion for small tenders, pilot boats, and harbor utility
vessels.
Pleasure Craft: Power for motor yachts and cabin cruisers requiring 30
hp class propulsion.
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