Yanmar 3GM30 Specifications
| Engine Model: Yanmar 3GM30 |
| Engine Type: 4-stroke inline 3-cylinder water-cooled diesel |
| Total Displacement: 58.2 cu.in (0.95 L) |
| Rated Engine Power: 27 Hp (20.1 kW) at 3600 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 3GM30 is a three-cylinder, vertical,
four-stroke marine diesel engine from the GM series. Yanmar designed
this compact powerplant as an auxiliary engine for mid-sized sailboats
ranging from 28 to 36 feet in length. The Yanmar 3GM30 produces 20.1 kW
(27 hp) at 3600 rpm for maximum output, with a continuous rating of 17.9
kW (24 hp) at 3400 rpm.
The engine uses indirect injection with a swirl pre-combustion chamber,
a system that provides smooth operation and reduced noise compared to
direct injection designs. The compression ratio is set high at 23.0:1,
ensuring reliable cold starting. Two cooling variants exist. The
standard 3GM30 uses direct seawater cooling, where raw water circulates
through the engine block.
The 3GM30F variant employs indirect freshwater cooling with a heat
exchanger, using antifreeze coolant in the engine and seawater in a
separate circuit. The engine starts via a 12V electric starter motor
rated at 1.0 kW, with older models featuring a manual hand-crank backup.
A 55-amp alternator charges the vessel's batteries. Two transmission
options are available: Kanzaki KM3P or KM3A mechanical cone clutch
gearboxes with reduction ratios of 2.36, 2.61, or 3.20 forward, and the
SD20 saildrive unit with a 2.64 reduction ratio for direct mounting to a
sail drive leg.
The Yanmar 3GM30 is a three-cylinder, four-stroke, vertical water-cooled
diesel engine. Total displacement measures 0.954 liters, equivalent to
954 cc or 58.2 cubic inches. Bore is 75 mm (2.95 in) with a stroke of 72
mm (2.83 in), producing a slightly oversquare configuration. The
combustion system uses indirect injection with a swirl pre-combustion
chamber. The compression ratio is 23.0:1. Aspiration is naturally
aspirated without turbocharging. Maximum output reaches 20.1 kW (27 hp)
at 3600 rpm.
Continuous output is 17.9 kW (24 hp) at 3400 rpm. Maximum torque is 5.6
kg-m, equivalent to 54.9 Nm (40.5 lb-ft), achieved at 2800 rpm. The
firing order is 1-3-2-1, a repeating cycle for the three cylinders.
Specific fuel consumption at maximum output is 215 grams per
horsepower-hour, representing 289 grams per kilowatt-hour. Dry weight of
the engine only is 130 kg (286 lb). Dry weight with the KM3A or KM3P
gearbox attached is 138 kg (304 lb). Dry weight with the SD20 saildrive
unit is approximately 145 kg (320 lb). The electrical system operates at
12V DC.
The cylinder block is constructed from cast iron with an inline
three-cylinder arrangement. The block is a single casting with integral
cylinder bores, meaning no replaceable cylinder liners are used. The
bores are precision-machined directly into the parent cast iron material
and finished with a cross-hatch hone pattern. This parent bore design
reduces manufacturing complexity and eliminates liner sealing issues
found in wet or dry liner engines. The cylinder block incorporates four
main bearing webs with reinforced bulkheads to support the crankshaft.
The block deck surface is machined flat to accept the cylinder head
gasket. Mounting pads are cast into the block for the fuel injection
pump, starter motor, alternator, and water pump. An oil pan rail is
machined on the lower face of the block. The block includes a
side-mounted oil filter housing and a dipstick tube port. On raw water
cooled versions (3GM30), seawater circulates directly through passages
cast into the block. On freshwater cooled versions (3GM30F), a mixture
of antifreeze and water circulates through the block, while seawater
flows through the heat exchanger only.
A single cast-iron cylinder head spans all three cylinders. The head
incorporates a cross-flow design with intake ports on one side and
exhaust ports on the opposite side. The valvetrain operates as an
overhead valve (OHV) configuration with two valves per cylinder - one
intake and one exhaust - for a total of six valves. A camshaft located
within the cylinder block actuates the valvetrain.
Pushrods transfer motion through vertical bores in the cylinder head to
rocker arms mounted on a steel shaft. Hardened valve seat inserts are
pressed into the cylinder head, with exhaust seats manufactured from a
heat-resistant nickel-chromium alloy. Valve guides are pressed-in
cast-iron sleeves. Valve lash is adjustable using a screw-and-locknut
mechanism on each rocker arm.
The indirect injection system includes a swirl pre-combustion chamber
for each cylinder, located within the cylinder head. Each pre-combustion
chamber is a precision-machined insert made from heat-resistant steel.
This chamber receives the fuel injector nozzle and creates intense swirl
motion to mix fuel with air before combustion propagates into the main
cylinder. The cylinder head gasket is a steel laminate design. Six head
bolts provide clamping force.
The fuel system uses mechanical indirect injection with a
distributor-type injection pump. A mechanical diaphragm-type lift pump
mounted on the cylinder block draws fuel from the tank through a primary
spin-on filter with a water separator. The lift pump includes a manual
priming lever for bleeding air from the system. The distributor-type
injection pump is driven by the engine timing gears. The pump contains a
single plunger that distributes fuel to each cylinder in the correct
firing order.
A mechanical centrifugal governor integrated into the pump regulates
fuel delivery based on engine speed and load. The governor includes
low-idle and high-speed limiting functions. A fuel shutoff solenoid or a
manual shutoff lever stops the engine by cutting fuel supply. Three
high-pressure steel injection lines carry fuel from the pump to the
injectors.
Each injector is a pintle-type nozzle designed specifically for indirect
injection systems, producing a single hollow-cone spray. Injectors are
installed in the cylinder head and positioned above each pre-combustion
chamber. A fuel return line routes excess fuel and injector leakage back
to the fuel tank. The system operates at lower injection pressures than
direct injection engines, reducing internal component stress.
The lubrication system is a forced-feed design using a trochoid-type oil
pump. The trochoid pump consists of an inner rotor mounted on the
camshaft and an outer rotor. This pump type provides a compact,
high-volume design with few moving parts. Oil is drawn from the oil pan
through a pick-up tube fitted with a coarse mesh strainer. Total oil
capacity is 2.7 liters, equivalent to 2.9 U.S. quarts. A spin-on
full-flow oil filter is mounted on the side of the cylinder block. The
filter incorporates an integral bypass valve that opens when the filter
element becomes restricted.
A pressure relief valve limits maximum oil pressure. The system supplies
lubricant to the four main bearings, three connecting rod bearings,
camshaft bearings, rocker arm assembly, timing gears, and the injection
pump driveshaft. Operating oil pressure at rated speed is maintained
between 275 and 345 kPa (40 and 50 psi). The oil pan is constructed from
stamped steel and includes a drain plug with a magnetic insert to
capture ferrous wear particles. Recommended oil grade is SAE 15W-40 for
most operating conditions.
Two distinct cooling systems exist for the 3GM30 and 3GM30F variants.
Standard 3GM30 (Raw Water Cooling): Seawater is drawn through a strainer
by a flexible impeller-type pump mounted on the front of the engine.
Seawater circulates directly through passages cast into the cylinder
block and cylinder head, then exits through the exhaust elbow to cool
the exhaust gases. No heat exchanger or antifreeze is used.
A wax-pellet thermostat located in a housing on the cylinder head
regulates seawater flow. The thermostat begins to open at 71°C (160°F)
and reaches full open at 82°C (180°F). 3GM30F (Freshwater Cooling): A
sealed freshwater circuit containing antifreeze and corrosion inhibitor
circulates through the engine block and cylinder head. A centrifugal
freshwater pump is belt-driven from the crankshaft.
A wax-pellet thermostat begins opening at 82°C (180°F) and reaches full
open at 95°C (203°F). Freshwater passes through a shell-and-tube heat
exchanger where seawater absorbs the heat before discharging overboard.
A separate flexible impeller-type seawater pump supplies cooling water
to the heat exchanger. Both variants use a raw water pump with a
neoprene impeller that requires periodic inspection and replacement.
| Intake and Exhaust Systems |
Air Intake System: Ambient air passes through a dry-type air cleaner
mounted directly on the intake manifold. The intake manifold distributes
air evenly to each cylinder head intake port. No turbocharger or
aftercooler is present.
Exhaust System: A cast-iron exhaust manifold collects gases from all
three cylinders. The manifold connects to a water-cooled exhaust elbow.
Seawater from the cooling system injects into this elbow, mixing with
exhaust gases to cool them before they exit through the vessel's exhaust
hose and stern outlet.
The electrical system operates at 12V DC. A gear-reduction starter motor
rated at 1.0 kW is mounted on the flywheel housing. A belt-driven
alternator produces charging current with a standard output of 55 amps.
Glow plugs are installed in the cylinder head, one per cylinder, located
within each pre-combustion chamber.
A glow plug relay controlled by a key switch or push button manages
pre-heat duration. Older models include a manual hand-crank backup
starting system, with a crank socket on the front of the crankshaft.
Engine length measured from the front cover to the flywheel housing
mounting face is 735 mm (28.9 in). Width measured across the widest
points, including the injection pump and exhaust manifold, is 455 mm
(17.9 in). Height measured from the oil pan rail to the top of the
rocker arm cover is 495 mm (19.5 in).
Dry weight of the engine only, excluding transmission, oil, and coolant,
is 130 kg (286 lb). Dry weight with the Kanzaki KM3A or KM3P gearbox is
138 kg (304 lb). Dry weight with the SD20 saildrive unit is 145 kg (320
lb). The weight with a full oil charge and coolant adds 5 kg (11 lb).
The shipping weight on a pallet with protective packaging is 160 kg (353
lb).
Engine Oil: Capacity: 2.7 l (2.9 U.S. qt). Oil change interval: 100
hours or annually. Recommended grade: SAE 15W-40 or SAE 10W-30. Oil
Filter: Spin-on full-flow type. Replace at every oil change. Coolant
(3GM30F only): Freshwater capacity: approximately 2.5 l (2.6 U.S. qt).
Change interval: 500 hours or 2 years. Antifreeze concentration: 40 to
50 percent. Raw Water Pump: Flexible impeller. Inspect at 200 hours.
Replace at 500 hours or annually.
Fuel Filter: Primary spin-on with water separator. Replacement interval:
250 hours. Secondary Fuel Filter (on injection pump): Replace at 250
hours. Air Cleaner: Dry paper element. Clean at 250 hours. Replace at
500 hours. Valve Lash (Cold): Intake: 0.20 mm (0.008 in). Exhaust: 0.20
mm (0.008 in). Valve Clearance Check Interval: 500 hours or 2 years. Low
Idle Speed: 850 to 950 rpm. High Idle Speed (No Load): 3750 to 3850 rpm.
Thermostat (Raw Water): Begins opening at 71°C (160°F). Fully open at
82°C (180°F). Thermostat (Freshwater): Begins opening at 82°C (180°F).
Fully open at 95°C (203°F). Injector Service: Inspect and test opening
pressure every 1000 hours. Glow Plugs: Resistance check at 500 hours.
Replace if open circuit. Engine Mounts: Inspect for cracking and sagging
at 1000 hours. Heat Exchanger (3GM30F): Zinc anode inspection at 250
hours. Replace when reduced to 50 percent.
Cylinder Head Bolts (M10 x 1.25): 30 Nm (22 lb-ft).
Connecting Rod Cap Nuts (M8 x 1.0): 35 Nm (26 lb-ft).
Main Bearing Cap Bolts (M10 x 1.25): 50 Nm (37 lb-ft).
Flywheel Bolts (M10 x 1.25): 45 Nm (33 lb-ft).
Crankshaft Pulley Bolt (M14 x 1.5): 90 Nm (66 lb-ft).
Camshaft Thrust Plate Bolts (M6 x 1.0): 12 Nm (9 lb-ft).
Rocker Arm Shaft Support Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Rocker Arm Adjustment Lock Nut (M6 x 1.0): 10 Nm (7 lb-ft).
Valve Cover Nuts (M6 x 1.0): 8 Nm (6 lb-ft).
Injection Pump Mounting Nuts (M8 x 1.25): 20 Nm (15 lb-ft).
Injection Lines (High Pressure) (M12 x 1.5): 18 Nm (13 lb-ft).
Injector Hold-Down Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Glow Plugs (M10 x 1.0): 15 Nm (11 lb-ft).
Oil Pan Drain Plug (M12 x 1.5): 30 Nm (22 lb-ft).
Starter Motor Mounting Bolts (M10 x 1.25): 35 Nm (26 lb-ft).
Alternator Pivot Bolt (M8 x 1.25): 20 Nm (15 lb-ft).
Raw Water Pump Mounting Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Thermostat Housing Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Exhaust Manifold Nuts (M8 x 1.25): 22 Nm (16 lb-ft).
Intake Manifold Bolts (M8 x 1.25): 20 Nm (15 lb-ft).
Engine Mount Bracket Bolts (M10 x 1.25): 40 Nm (30 lb-ft).
The Yanmar 3GM30 engine serves exclusively in marine applications.
Sailboats (Auxiliary Power): Mid-sized sailboats from 28 to 36 feet
length overall (LOA). Common installations include Beneteau First 305,
310, and 325 models. Catalina 30, 309, and 315 sailboats. Hunter 28.5,
29.5, and 30.5 models. Jeanneau Sun Odyssey 30i, 32i, and 34.2. Pearson
30, 31, and 32. Islander 30 and 32. Ericson 30 and 32. Caliber 30 and
33.
Powerboats (Small Displacement Vessels): Small displacement cruisers and
pocket trawlers under 30 feet. Transmission Configurations: Kanzaki KM3A
or KM3P mechanical cone clutch gearbox with reduction ratios of 2.36:1,
2.61:1, or 3.20:1 forward rotation. These gearboxes provide a reverse
rotation for maneuvering. Yanmar SD20 saildrive unit with a 2.64:1
reduction ratio.
The SD20 mounts directly to the engine flywheel housing and incorporates
a vertical drive leg extending through the hull bottom, eliminating the
need for a traditional shaft, stuffing box, and rudder offset. This
engine also appears in commercial aquaculture vessels and small
workboats requiring reliable auxiliary power. Many marine hydraulic
systems, including bow thrusters and deck winches, use the 3GM30 as a
hydraulic pump driver on larger vessels.
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