Yanmar 3QM30 Specifications
| Engine Model: Yanmar 3QM30 |
| Engine Type: 4-stroke inline 3-cylinder water-cooled diesel |
| Total Displacement: 100 cu.in (1.64 L) |
| Rated Engine Power: 33 Hp (24.6 kW) at 2800 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 3QM30 is a 1.6-liter,
three-cylinder, naturally aspirated four-stroke marine diesel engine
produced by Yanmar. This engine belongs to the QM series, which includes
the 2QM20 two-cylinder variant and the 3QM30 three-cylinder model. The
3QM30 was designed for marine propulsion applications in sailboats and
powerboats, offering a combination of reliability, mechanical
simplicity, and fuel efficiency. The engine is available in several
configurations: the direct seawater-cooled 3QM30 and 3QM30H, and the
fresh water-cooled 3QM30F model equipped with a heat exchanger.
The Yanmar 3QM30 utilizes a swirl pre-combustion chamber (indirect
injection) system rather than direct injection. This IDI design provides
smoother combustion, reduced noise, and improved low-speed operation
compared to direct injection engines of its era. With a continuous
rating of 30 hp at 2,600 rpm and a one-hour rating of 33 hp at 2,800
rpm, the 3QM30 was a popular choice for cruising yachts and displacement
vessels.
The engine features a 12 V electric starter with a manual hand-crank
backup, a forced lubrication system with a trochoid pump, and a
counterclockwise rotation viewed from the flywheel (stern). The dry
weight ranges from 260-310 kg depending on gearbox and cooling
configuration.
Engine Type: 4-stroke, vertical, 3-cylinder, water-cooled diesel.
Displacement: 1.642 L (100.2 cu.in).
Bore x Stroke: 88.0 mm x 90.0 mm (3.46 in x 3.54 in).
Compression Ratio: 20.0:1.
Combustion System: Swirl pre-combustion chamber (indirect injection).
Aspiration: Naturally aspirated.
Continuous Rating: 30 hp (22.4 kW) at 2,600 rpm.
One-Hour Rating: 33 hp (24.6 kW) at 2,800 rpm.
Maximum Torque: 9.5 kg-m (68.7 lb-ft) at 2,000 rpm.
Cruising RPM Range: 2,200-2,400 rpm.
Maximum RPM: 3,000-3,200 rpm depending on source.
Idle RPM: 800 rpm.
Valvetrain: Overhead valve (OHV), pushrod-actuated, 2 valves per
cylinder.
Valve Clearance (Cold - Intake): 0.40 mm (0.016 in).
Valve Clearance (Cold - Exhaust): 0.40 mm (0.016 in).
Fuel System: Indirect injection with in-line injection pump.
Injection Pressure: 100-110 kg/cm2 (1,422-1,564 psi).
Cooling System: Direct seawater (3QM30/3QM30H).
Cooling System: Freshwater with heat exchanger (3QM30F).
Lubrication System: Forced lubrication with trochoid pump.
Starting System: Electric start (12 V) with manual hand-crank backup.
Starter Motor Power: 12 V, 1.8 kW.
Direction of Rotation: Counterclockwise viewed from flywheel (stern).
The cylinder block is constructed from cast iron with a vertical, inline
3-cylinder configuration. The block features a deep-skirt design
providing support for the main bearing webs and reducing engine
vibration. The cylinder bores are machined directly into the cast iron
block. Four main bearings support the crankshaft. A gear housing
attaches to the front of the block, containing the camshaft drive gears.
The block incorporates a full-length water jacket surrounding each
cylinder. Integrated oil galleries are cast into the block structure to
supply pressurized oil to the main bearings, connecting rod bearings,
and the valve train components. The crankcase is sealed with an oil pan.
The block includes mounting bosses for the starter motor, alternator,
and cooling pumps.
The cylinder head is a separate cast iron unit bolted to the block. The
swirl pre-combustion chamber (indirect injection) design incorporates a
small pre-chamber where fuel combustion begins before expanding into the
main cylinder. This IDI design promotes smoother combustion, reduced
noise, and improved low-speed operation. The valvetrain operates with an
overhead valve (OHV) configuration using pushrods and rocker arms
actuated by a camshaft located in the cylinder block.
Each cylinder is served by two valves: one intake valve and one exhaust
valve. The valve clearance requires periodic manual adjustment. The cold
valve clearance specification for both intake and exhaust valves is 0.40
mm (0.016 in). The exhaust manifold is bolted to the cylinder head, with
a silencer attached to the manifold outlet.
The fuel system on the 3QM30 is an indirect injection design with an
in-line injection pump. The injection pump is driven by the engine's
gear train and supplies fuel under high pressure to the injection valves
(injectors). The injection pressure is set to 100-110 kg/cm2
(1,422-1,564 psi).
The indirect injection process begins with fuel injection into the swirl
pre-combustion chamber, where partial combustion occurs before the
burning mixture expands into the main cylinder. A mechanical governor
controls engine speed. The fuel system includes a fuel filter to protect
the injection components from contaminants. A manual fuel feed pump
(primer pump) is provided for bleeding air from the fuel system after
filter changes.
The lubrication system is a forced-feed, fully pressurized design using
a trochoid-type oil pump. The oil pump draws oil from the oil pan
through a screened pickup tube. The oil is forced through a spin-on oil
filter before distribution to the main galleries.
From the main galleries, pressurized oil is supplied to the main
bearings, connecting rod bearings, camshaft bearings, and the valve
train components. The total engine oil capacity is 7.0 L (7.4 qt)
including the oil filter. For the KH18 gearbox, the oil capacity is 1.2
L (1.3 qt). A dipstick provides a convenient method for checking the oil
level.
The cooling system configuration varies by model. The 3QM30 and 3QM30H
use direct seawater cooling, where raw water is drawn from outside the
vessel, circulated through the engine block and cylinder head, and
expelled with the exhaust gases. The 3QM30F uses an indirect freshwater
(closed) cooling system with a heat exchanger. In this configuration, a
camshaft-driven seawater pump circulates raw water through the heat
exchanger.
A separate fresh water pump circulates coolant (fresh water mixed with
antifreeze) through the engine block and cylinder head. A wax-type
thermostat maintains engine operating temperature. The heat exchanger on
some installations is mounted on the bell housing above the transmission
or on the starboard side of the engine compartment. Both types of heat
exchangers use sacrificial pencil anodes to prevent corrosion.
Starting System: The engine is equipped with an electric starting system
operating at 12 V. A key switch panel controls the starter motor. A
manual hand-crank mechanism is provided as a backup starting method for
emergency situations.
Electrical System: The alternator (generator) is belt-driven and
provides 12 V electrical power for the starter motor, instruments, and
battery charging. The instrument panel includes oil pressure and coolant
temperature gauges plus audible alarms.
Exhaust System: The exhaust system uses wet exhaust injection. Seawater
from the cooling system is injected into the exhaust mixing elbow. This
water cools the exhaust gases before they pass through the muffler and
are expelled overboard. A siphon break must be installed in the system
to prevent seawater from backing through the exhaust line and entering
the engine.
Transmission: The 3QM30 is paired with a Kanzaki reduction and reversing
gear (KH18 series). The gearbox uses a friction clutch system. The
transmission oil capacity is 1.2 L (1.3 qt).
Engine Mass (Dry without gearbox): 260-310 kg (573-683 lb).
Overall Length: 770-800 mm (30.3-31.5 in) depending on gearbox.
Overall Width: 480-540 mm (18.9-21.3 in).
Overall Height: 620-640 mm (24.4-25.2 in).
Engine Oil Grade: SAE 30 or SAE 15W-40 rated for marine diesel engines.
Engine Oil Capacity: 7.0 L (7.4 qt) including oil filter.
Gearbox Oil Capacity: 1.2 L (1.3 qt) for KH18 gearbox.
Coolant Type (3QM30F): Ethylene glycol antifreeze, 50/50 mixture with
distilled water.
Coolant Capacity (3QM30F): Refer to factory operation manual.
Fuel System: Indirect injection, mechanical in-line injection pump.
Injection Pressure: 100-110 kg/cm2 (1,422-1,564 psi).
Valve Clearance (Cold - Intake): 0.40 mm (0.016 in).
Valve Clearance (Cold - Exhaust): 0.40 mm (0.016 in).
Idle RPM: 800 rpm.
Cruising RPM: 2,200-2,400 rpm.
Maximum RPM: 3,000-3,200 rpm.
Starter Motor: 12V, 1.8 kW.
Alternator Output: 12V, 35 A.
Glow Plugs: 12 V, for cold-start assistance.
Cylinder Head Bolts: 88 to 93 Nm (65 to 69 lb-ft).
Connecting Rod Bolts: 44 to 49 Nm (32 to 36 lb-ft).
Main Bearing Cap Bolts: 88 to 93 Nm (65 to 69 lb-ft).
Flywheel Bolts (to Crankshaft Flange): 60 to 65 Nm (44 to 48 lb-ft).
Rocker Arm Shaft Bracket Bolts: 19 to 24 Nm (14 to 18 lb-ft).
Intake Manifold Nuts: 12 to 14 Nm (9 to 10 lb-ft).
Exhaust Manifold Nuts: 19 to 24 Nm (14 to 18 lb-ft).
Injection Nozzle Hold-Down Bolts: 59 to 64 Nm (44 to 47 lb-ft).
Glow Plugs: 12 to 15 Nm (9 to 11 lb-ft).
Water Pump Mounting Bolts: 19 to 24 Nm (14 to 18 lb-ft).
Oil Pan Bolts: 9 to 12 Nm (7 to 9 lb-ft).
Timing Gear Cover Bolts: 9 to 12 Nm (7 to 9 lb-ft).
Engine Mount Bracket Bolts (to Block): 44 to 49 Nm (32 to 36 lb-ft).
Starter Motor Mounting Bolts: 29 to 34 Nm (21 to 25 lb-ft).
Alternator Mounting Bolts: 19 to 24 Nm (14 to 18 lb-ft).
The Yanmar 3QM30 was designed exclusively for marine propulsion
applications.
Sailboats:
Tayana 37 (standard engine in many production versions).
Morgan 38.
Hunter 37 Cherubini (3QM30 and 3QM30F variants).
Various other cruising sailboats of the 1970s-1980s.
Powerboats:
Small displacement cruisers.
Commercial vessels (small workboats).
Repower Applications:
Used as a replacement engine for older Yanmar QM series engines.
The QM series has been superseded by the 3YM20 and 3YM30 modern engines,
which feature simplified maintenance and meet newer emission standards.
The 3QM30 requires periodic maintenance including valve clearance
checks, injection pressure verification, and fuel system servicing as
outlined in the Yanmar 2QM20/3QM30 service workshop manual. Parts
availability remains reasonable through Yanmar distributors and
aftermarket suppliers, though some components require professional
rebuilding. The engine is recognized for its long service life when
properly maintained.
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