Yanmar 3YM30 Specifications
| Engine Model: Yanmar 3YM30 |
| Engine Type: 4-stroke inline 3-cylinder water-cooled diesel |
| Total Displacement: 68 cu.in (1.12 L) |
| Rated Engine Power: 29 Hp (21.3 kW) at 3600 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 3YM30 is a 3-cylinder, naturally
aspirated marine diesel engine from the YM series. Designed for
sailboats and small powerboats, this engine features a compact profile
and fresh-water cooling as standard. Produced from the early 2000s
onward, the 3YM30 represents Yanmar’s engineering approach to auxiliary
marine power, prioritizing reliability, low vibration, and ease of
installation in confined engine compartments.
The YM series replaced the earlier GM series, offering reduced weight
and improved fuel efficiency. The 3YM30’s three-cylinder configuration
provides inherent balance characteristics that contribute to smooth
operation, a significant advantage for cruising sailboats. The engine’s
indirect injection combustion system with swirl chamber reduces
combustion noise and improves cold-start performance, making it suitable
for pleasure craft and light commercial marine applications.
The Yanmar 3YM30 engine is recognized for its smooth operation, compact
dimensions, and reliable starting characteristics. The indirect
injection system provides quieter running than direct injection diesels
of comparable displacement, a valued attribute for overnight cruising
and anchorage maneuvers. The fresh-water cooling system with heat
exchanger isolates the engine block from seawater corrosion, extending
service life in saltwater environments. The three-cylinder configuration
produces a favorable torque curve, with peak torque delivered between
2,200 and 2,600 rpm, aligning with typical sailboat propeller curve
requirements.
The engine’s dry weight of 120 kg (265 lb) without gearbox simplifies
installation and contributes to favorable vessel weight distribution.
The 12V/60A alternator provides sufficient charging capacity for marine
electrical systems, with an 80A optional upgrade for vessels with higher
electrical demands. Service considerations include regular valve
clearance checks (0.2 mm cold for both intake and exhaust) and attention
to the indirect injection system’s injector pressures.
Engine Type: Vertical inline 3-cylinder, 4-cycle, water-cooled marine
diesel engine.
Family: Yanmar YM series.
Displacement: 1.115 liters (68.0 cu.in), equivalent to 1.1 L.
Bore: 76.0 mm (2.99 in).
Stroke: 82.0 mm (3.23 in).
Compression Ratio: 18.5:1 to 19.5:1, varying with injector calibration.
Combustion System: Indirect injection with swirl (pre-combustion)
chamber.
Aspiration: Naturally aspirated.
Firing Order: 1-2-3.
Rotation (from flywheel end): Counter-clockwise.
Rated Speed Range: 3,000-3,600 rpm.
Maximum Output (Crankshaft): 21.3 kW (29 hp) at 3,600 rpm.
Continuous Rating (Marine propulsion): 18.1 kW (24.3 hp) at 3,490 rpm.
Maximum Torque: 64 Nm (47 lb-ft) @ 2,200-2,600 rpm.
Cruising RPM Range: 3,000-3,200 rpm.
Low Idle Speed: 800-850 rpm.
The cylinder block is constructed from cast iron with a closed-deck
design. The block features integral cylinder bores cast directly into
the iron, machined with a honed finish for piston ring compatibility.
The three-cylinder block incorporates four main bearing webs supporting
a forged steel or nodular cast-iron crankshaft with four main bearings.
The crankshaft is induction-hardened at the journal surfaces and
incorporates four counterweights to control vibration inherent to
three-cylinder engine configurations.
The block features a deep-skirt design extending below the crankshaft
centerline, with reinforced bulkheads at each main bearing location.
Integrated oil galleries within the block supply the crankshaft main
bearings, connecting rod bearings, and camshaft bearings. The timing
gear housing is integrated into the front of the block. An
engine-mounted lifting bracket is cast into the block for service
removal.
The cylinder head is manufactured from cast iron and houses the overhead
valve (OHV) arrangement with two valves per cylinder (six total). The
cross-flow design positions intake ports on one side and exhaust ports
on the opposite side. Intake valves measure 30.0 mm (1.18 in) in
diameter, while exhaust valves measure 27.0 mm (1.06 in). The valvetrain
consists of a single camshaft located in the cylinder block, operating
the valves through hardened pushrods and stamped steel rocker arms.
Valve seat inserts are replaceable, extending cylinder head service
life. Valve clearance is adjusted by a screw and locknut on each rocker
arm. Swirl chambers (pre-combustion chambers) are pressed into the
cylinder head, one per cylinder, promoting turbulent combustion and
reducing diesel knock at idle speeds. The cylinder head is secured by
four head bolts per cylinder (12 total), requiring a multi-step torque
sequence. The cylinder head incorporates the freshwater coolant passages
surrounding the swirl chambers.
The fuel system employs a mechanical indirect injection architecture
using an in-line injection pump (Bosch or Yanmar-built). The injection
pump is flange-mounted to the timing gear housing and driven by the
engine's gear train. A mechanical governor, integrated into the
injection pump, maintains engine speed under varying loads through a
centrifugal weight mechanism connected to the throttle lever.
High-pressure injection lines deliver fuel to pintle-type injectors
mounted in each cylinder head. Injector opening pressure is factory set
between 120 and 130 bar (1,707-1,849 psi). The indirect injection system
sprays fuel into the swirl chamber where air-fuel mixing begins before
combustion proceeds into the main cylinder.
A mechanical fuel feed pump, mounted on the cylinder block and actuated
by an eccentric lobe on the camshaft, draws fuel from the tank and
supplies it through a spin-on primary fuel filter and a secondary fuel
filter to the injection pump. A manual primer lever on the feed pump
allows bleeding air from the system after filter changes.
The lubrication system is a forced-feed, wet-sump type utilizing a
trochoid-type oil pump mounted to the front timing gear housing. The
trochoid pump design provides smooth, pulseless oil flow with reduced
noise compared to gear pumps. The pump is driven by the camshaft gear,
ensuring immediate oil pressure upon startup. Oil is drawn from a cast
aluminum oil pan through a strainer before pressurization. A full-flow
spin-on oil filter is mounted externally on the cylinder block.
The system supplies lubricant to the crankshaft main bearings,
connecting rod bearings, camshaft bearings, timing gears, pushrods,
rocker shaft, and valve tips. The oil pump incorporates a pressure
relief valve set between 2.5 and 3.5 bar (36-51 psi) at rated speed. The
oil pan capacity of 2.8 liters (3.0 qt) is designed to minimize the
engine’s vertical height for installation under sailboat cockpit floors.
A dipstick on the side of the block indicates oil level.
The cooling system is a freshwater (closed-circuit) cooled system with a
heat exchanger, isolating the engine block from seawater corrosion. A
centrifugal fresh-water pump, belt-driven from the crankshaft pulley,
circulates coolant through the cast-iron cylinder block and cast-iron
cylinder head. A wax-type thermostat with a rated opening temperature of
70°C (158°F) or 82°C (180°F) regulates the engine operating temperature,
depending on application. The heat exchanger is a tube-in-shell design
mounted on the engine.
Seawater is drawn through a seacock and strainer, circulated by a
rubber-impeller seawater pump, and passed through the heat exchanger to
remove heat from the freshwater circuit before being discharged
overboard. A belt-driven cooling fan is not present; heat rejection
occurs entirely through the heat exchanger. The freshwater capacity is
4.5 liters (4.8 qt) inclusive of the engine block and heat exchanger. A
seawater-cooled oil cooler is integrated into the lubrication system on
some variants.
| Intake and Exhaust Systems |
Intake System: Air is drawn through a flame arrestor (marine safety
device) or a dry-type paper element air filter before entering the
intake manifold. The intake manifold is cast separately and mounts to
the side of the cylinder head.
Exhaust System: A cast-iron exhaust manifold collects gases and directs
them to a water-injected exhaust elbow. Seawater is injected into the
exhaust elbow to cool exhaust gases before they pass through the exhaust
hose and waterlock/silencer system, preventing heat damage to hoses and
components.
Timing System: The camshaft is driven by a gear train from the
crankshaft. Hardened steel timing gears at the front of the engine
provide fixed timing without belts or chains requiring replacement. The
gear train sequentially drives the crankshaft gear, idler gear, camshaft
gear, and injection pump gear. Timing marks on each gear must align
during assembly. No timing tensioner is present due to the fixed gear
arrangement.
Starting System: A 12-volt electric starter motor (1.2 kW) is mounted to
the flywheel housing, engaging a ring gear on the flywheel. A 12V/60A
alternator (standard) or 12V/80A alternator (optional) maintains battery
charge and supplies electrical power for navigation equipment, lighting,
and vessel systems. The electrical system is designed for marine
environments with corrosion-resistant terminals and sealed connectors.
Glow Plug System: Individual pencil-type glow plugs are mounted in each
cylinder head, projecting into the swirl chamber. Glow plug operation is
controlled by a timer relay, with pre-heat times of 5-15 seconds
depending on ambient temperature. A glow indicator lamp on the helm
signals when starting can commence.
Overall Engine Length: 590 mm (23.2 in) from front cover to flywheel
housing.
Overall Engine Width: 500 mm (19.7 in).
Overall Engine Height: 560 mm (22.0 in) from oil pan bottom to rocker
cover top.
Dry Weight (without gearbox): 120 kg (265 lb).
Dry Weight (with SD20 saildrive gearbox): 145 kg (320 lb).
Dry Weight (with KM2P-1 reverse gear): 135 kg (298 lb).
Engine Oil Capacity (with Filter): 2.8 liters (3.0 U.S. qt, 2.5 imperial
qt). Engine Oil Specification: API CD, CE, CF, or CI-4 grade; SAE 15W-40
or SAE 10W-30 viscosity recommended. SAE 30 single-grade may be used in
warm climates. Low-ash oil is recommended for extended engine life. Oil
Change Interval: 200 operating hours or annually under normal
conditions; 100 hours under severe service (frequent short runs or heavy
loads).
Coolant Capacity (Freshwater): 4.5 liters (4.8 qt) inclusive of the
engine block and heat exchanger. Coolant Specification: Ethylene
glycol-based antifreeze with corrosion inhibitors for diesel engines. A
propylene glycol coolant may be used where environmental regulations
require non-toxic fluids. Thermostat Opening Temperature: 70°C (158°F)
or 82°C (180°F) depending on configuration.
Seawater Pump Impeller Inspection Interval: 200 operating hours or
annually. Seawater Pump Impeller Replacement Interval: 500 operating
hours or 2 years. Fuel Filter Replacement Interval: 250 operating hours
or annually. Primary Fuel Filter (Racor or similar) Element Replacement:
250 operating hours or when visible contamination is present.
Valve Clearance (Cold): Intake: 0.20 mm (0.008 in); Exhaust: 0.20 mm
(0.008 in). Adjustment is performed by loosening the rocker arm locknut
and turning the adjusting screw while holding the appropriate feeler
gauge. Valve Clearance Inspection Interval: 400 operating hours or
annually. Heat Exchanger Service: Inspection and cleaning of seawater
tubes at 1,000 operating hours or 2 years. Zinc anodes in the heat
exchanger must be inspected and replaced when corroded (annually in
saltwater).
Injector Inspection Interval: 800 operating hours for opening pressure
testing, spray pattern inspection, and flow testing. Injection Pump
Timing: Static timing set at 10-12 degrees before top dead center,
verified by aligning marks on the pump flange and timing gear housing or
by using a dial indicator on the pump plunger. Fuel Injection Pressure:
120-130 kgf/cm2 (1,707-1,849 psi, 11.8-12.7 MPa). Glow Plug Resistance:
0.5-1.0 ohm at 20°C (68°F).
Cylinder Head Bolts, Step 1: 20 Nm (2.0 kgf-m, 15 lb-ft).
Cylinder Head Bolts, Step 2: 40 Nm (4.1 kgf-m, 30 lb-ft).
Cylinder Head Bolts, Step 3: 60 Nm (6.1 kgf-m, 44 lb-ft).
Cylinder Head Bolts, Step 4: 80 Nm (8.2 kgf-m, 59 lb-ft).
Main Bearing Cap Bolts: 50 Nm (5.1 kgf-m, 37 lb-ft).
Connecting Rod Cap Bolts: 40 Nm (4.1 kgf-m, 30 lb-ft).
Flywheel Bolts: 45 Nm (4.6 kgf-m, 33 lb-ft).
Crankshaft Pulley Bolt: 100 Nm (10.2 kgf-m, 74 lb-ft).
Camshaft Bearing Cap Bolts: 16 Nm (1.6 kgf-m, 12 lb-ft).
Rocker Arm Shaft Bolts: 18 Nm (1.8 kgf-m, 13 lb-ft).
Intake Manifold Bolts: 15 Nm (1.5 kgf-m, 11 lb-ft).
Exhaust Manifold Nuts: 18 Nm (1.8 kgf-m, 13 lb-ft).
Injection Pump Mounting Nuts: 20 Nm (2.0 kgf-m, 15 lb-ft).
Injector Hold-Down Clamp Bolts: 15 Nm (1.5 kgf-m, 11 lb-ft).
Oil Filter (Spin-on Type): 12 Nm (1.2 kgf-m, 9 lb-ft).
Oil Pan Bolts: 12 Nm (1.2 kgf-m, 9 lb-ft).
Glow Plugs: 10 Nm (1.0 kgf-m, 7 lb-ft).
Starter Motor Mounting Bolts: 30 Nm (3.1 kgf-m, 22 lb-ft).
Alternator Mounting Bolts: 25 Nm (2.5 kgf-m, 18 lb-ft).
Freshwater Pump Mounting Bolts: 15 Nm (1.5 kgf-m, 11 lb-ft).
The Yanmar 3YM30 engine is utilized exclusively in marine propulsion
applications for sailboats and small powerboats.
Sailboats (Auxiliary Propulsion)
Beneteau Oceanis 31, 34, 37: Cruising sailboats with the 3YM30 as
std/opt auxiliary power.
Jeanneau Sun Odyssey 32, 35, 37: Sailboat range utilizing the 3YM30 for
auxiliary propulsion.
Hunter 31, 33, 36: American-built cruising sailboats.
Catalina 309, 315, 320: Sailboats from Catalina Yachts.
Dufour 325, 335, 365: European cruising yachts.
Hallberg-Rassy 31, 34: Swedish bluewater cruising yachts (optional
upgrade from 3YM20).
Moody 31, 35, 38: British-built cruising sailboats.
Island Packet 320, 350: Heavy displacement cruising sailboats.
Small Powerboats and Trawlers
Small displacement powerboats: 25-32 ft (7.6-9.8 m) semi-displacement
hulls.
Pilot house cruisers: Small coastal cruisers with diesel propulsion.
Downeast-style boats: Traditional lobster boat hulls converted for
pleasure use.
Light Commercial Marine
Small fishing vessels: Inshore fishing boats and gillnetters.
Workboats: Harbour utility vessels and small launches.
Rib (Rigid Inflatable Boats) for commercial use: Large RIBs for patrol
and personnel transport.
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