Yanmar 2YM15 Specifications
| Engine Model: Yanmar 2YM15 |
| Engine Type: 4-stroke 2-cylinder water-cooled diesel |
| Total Displacement: 34.8 cu.in (0.57 L) |
| Rated Engine Power: 13.6 Hp (10 kW) at 3600 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 2YM15 is a compact, two-cylinder,
four-stroke marine diesel engine from the Yanmar YM series. This engine
is specifically engineered for small sailboats (such as Beneteau First
210 and similar yachts up to 26 feet), daysailers, and small commercial
workboats. The Yanmar 2YM15 features freshwater cooling with a heat
exchanger, eliminating the need for direct raw water circulation through
the engine block. The indirect injection system uses a swirl
pre-combustion chamber, providing smooth operation, low noise, and
reduced vibration compared to direct injection engines of equivalent
displacement.
The engine is designed for high torque at low crankshaft speeds, which
is essential for maneuvering in harbors and maintaining steady headway
in adverse sea conditions. The YM series is recognized for its low fuel
consumption and compliance with stringent emission regulations,
including EU RCD 2, BSO II, and US EPA Tier 3. The 2YM15 is supplied
with either a KM2P-1 cone clutch marine gear or an SD25 saildrive unit.
Engine Type: 4-stroke, water-cooled, vertical inline diesel.
Number of Cylinders: 2.
Displacement: 570 cc (0.570 L / 34.8 cu.in).
Bore x Stroke: 70 mm x 74 mm (2.76 in x 2.91 in).
Combustion System: Indirect injection (swirl pre-combustion chamber).
Aspiration: Naturally aspirated.
Maximum Output (Crankshaft): 10.0 kW (13.6 hp) at 3600 rpm.
Continuous Rating (Crankshaft): 9.4 kW (12.8 hp) at 3489 rpm.
Maximum Torque: 28.5 Nm (21.0 lb-ft) at 2600 rpm.
Direction of Rotation: Counterclockwise viewed from the stern (flywheel
side).
Compression Ratio: 23.0:1.
Emission Compliance: EU RCD 2, BSO II, EMC; US EPA Tier 3.
Starting System: 12V DC electric start with 1.4 kW starter motor.
Alternator: 12V - 125A (125 amp rating).
Exhaust Pipe Diameter: 51 mm (2.0 in).
Fuel Consumption (Cruising): 1.0-1.2 L/h (0.26-0.32 gal/h) at moderate
load.
Dry Weight (Engine Only): 103 kg (227 lb).
Dry Weight (with KM2P-1 Gear): 113 kg (249 lb).
Dry Weight (with SD25 Saildrive): 134 kg (295 lb).
The cylinder block is manufactured from cast iron, providing a rigid and
vibration-damping foundation for the two-cylinder configuration. The
compact inline design minimizes the engine footprint for installation
under sailboat cockpit floors and in small engine compartments. The
block incorporates dry-type cylinder liners that are precision-machined
and not intended for routine replacement, reflecting the engine’s design
for long service life without major overhauls.
The water jacket surrounds each cylinder bore completely, ensuring
uniform heat dissipation from the indirect injection combustion process.
An oil gallery is cast into the block to supply pressurized lubricant to
the crankshaft main bearings, connecting rods, and camshaft bearings.
The block includes integrated mounting feet with rubber vibration
isolation mounts.
The cylinder head is constructed from cast aluminum alloy, reducing
overall engine weight for small vessel applications. The overhead valve
(OHV) arrangement uses a camshaft located in the cylinder block with
valve actuation via pushrods and rocker arms. Each cylinder receives two
valves: one intake and one exhaust. The indirect injection system
requires an additional component: a pre-combustion chamber (swirl
chamber) cast into the cylinder head for each cylinder.
This chamber receives the injected fuel, where initial combustion occurs
before the flame front propagates into the main cylinder. The valve
seats are manufactured from heat-resistant alloy steel, and valve guides
are press-fitted. The valvetrain requires periodic manual valve
clearance adjustment using a screw and locknut mechanism on each rocker
arm.
The fuel system is an indirect injection design using an inline
injection pump mounted on the engine side. A mechanical fuel feed pump,
driven by the camshaft, draws fuel from the tank through a primary fuel
filter. The injection pump delivers high-pressure fuel through steel
lines to the injection nozzles located in each cylinder head. Each
nozzle is positioned to spray fuel into the pre-combustion chamber
rather than directly into the cylinder bore.
A glow plug is installed in each pre-combustion chamber to heat incoming
air during cold starting. The glow plugs are controlled by a pre-heat
timer relay. A fuel filter with an integrated water separator is mounted
between the fuel tank and the feed pump. Fuel return lines route excess
fuel from the injection pump and nozzles back to the fuel tank.
The lubrication system is an enclosed, forced-feed pressurized design
using a trochoid oil pump. The trochoid pump, known for its compact size
and quiet operation, is mounted on the timing gear case and driven by
the crankshaft gear. Oil is drawn from the oil sump through a wire mesh
suction strainer. Pressurized oil passes through a full-flow spin-on oil
filter. From the filter, oil enters the main oil gallery.
The gallery distributes oil to the two main bearings, connecting rod
bearings, camshaft bearings, and timing gears. A drilled passage within
the cylinder block directs oil upward to the rocker arm shaft. The total
oil capacity is 2.0 liters (2.1 qt). The oil pan is a pressed steel
construction with a drain plug. A dipstick is provided for oil level
measurement. The engine is equipped with a closed crankcase ventilation
system.
The cooling system is a dual-circuit, freshwater-cooled (closed) design
with a heat exchanger. This system separates the engine’s internal
coolant from the external seawater. The freshwater circuit uses a
centrifugal water pump driven by the front accessory belt. Coolant
circulates through the cylinder block, cylinder head, and the freshwater
side of the heat exchanger. A thermostat housed on the cylinder head
regulates coolant flow to maintain operating temperature between 75-85°C
(167-185°F).
The seawater circuit uses a flexible impeller-type pump mounted on the
front of the engine. Seawater is drawn through a hull strainer and
seacock, then circulated through the seawater side of the heat exchanger
before being discharged into the exhaust injection elbow. The heat
exchanger is a shell-and-tube design mounted on the engine. A coolant
expansion tank with a pressure cap is integrated into the system.
| Intake and Exhaust Systems |
Intake System: The intake manifold is a cast aluminum plenum mounted on
the cylinder head. Air enters through a flame arrestor (for engine room
installations) or through a dry-type air cleaner. The naturally
aspirated engine draws air directly into the intake manifold without
forced induction.
Exhaust System: A water-cooled exhaust manifold is integrated with the
cylinder head. Exhaust gases pass through the manifold into a
water-injected exhaust elbow where seawater from the cooling system is
introduced. This water cools the exhaust gases and acts as a silencer.
The wet exhaust system discharges through a gooseneck fitting and a
waterlock muffler to prevent seawater siphoning back into the engine.
Electrical System: The 12V system includes a 1.4 kW starter motor and a
high-output 125A alternator. The alternator provides sufficient charging
capacity for multiple batteries on cruising sailboats. A pre-heat glow
plug controller, engine start-stop panel, and alarm system (oil
pressure, coolant temperature) are standard.
Marine Gear Options: The KM2P-1 marine gear is a mechanical cone clutch
transmission with forward reduction ratios of 2.21:1, 2.62:1, or 3.22:1.
Reverse reduction is 3.06:1. The SD25 saildrive unit is a constant mesh
gear with a dog clutch and a reduction ratio of 2.64:1. The saildrive
mounts directly under the engine and transmits power to a horizontally
mounted propeller.
Overall Length (Engine Only): 613 mm (24.1 in).
Overall Width: 463 mm (18.2 in).
Overall Height: 600 mm (23.6 in).
Dry Weight (Engine Only): 103 kg (227 lb).
Dry Weight (with KM2P-1 Gear): 113 kg (249 lb).
Dry Weight (with SD25 Saildrive): 134 kg (295 lb).
Engine Oil Capacity (with filter): 2.0 liters (2.1 qt).
Engine Oil Specification: API CF, CF-4, or CJ-4. SAE 15W-40, SAE 5W-30,
10W-30.
Oil Change Interval: 100 hours or 12 months, whichever arrives first.
Oil Filter Change Interval: Every 100 hours (with each oil change).
Fuel Filter Change Interval: 100 hours or 12 months.
Fuel Filter Water Drain: Check every 50 hours; drain when water is
present.
Coolant Capacity (Freshwater Circuit): 2.2 liters (2.3 qt).
Coolant Specification: Ethylene glycol-based antifreeze with corrosion
inhibitors.
Coolant Change Interval: 500 hours or 2 years.
Seawater Pump Impeller Change Interval: 200 hours or 12 months. Inspect
annually.
Valve Clearance (Cold, Intake): 0.15-0.20 mm (0.006-0.008 in).
Valve Clearance (Cold, Exhaust): 0.20-0.25 mm (0.008-0.010 in).
Valve Clearance Adjustment Interval: 200 hours or 2 years.
Idle Speed (in gear, warm engine): 850-900 rpm.
Glow Plug Pre-heat Time: 5-10 seconds depending on ambient temperature.
Sacrificial Anodes (Heat Exchanger): Inspect every 200 hours; replace
when 50% consumed.
Engine Mount Inspection: Every 200 hours.
Propeller Shaft Alignment: Check every 100 hours or annually.
Cylinder Head Bolts (Stage 1): 30 Nm (22 lb-ft).
Cylinder Head Bolts (Stage 2): 50 Nm (37 lb-ft).
Cylinder Head Bolts (Stage 3): 70 Nm (52 lb-ft) final pass.
Main Bearing Cap Bolts: 65 Nm (48 lb-ft).
Connecting Rod Cap Nuts: 35 Nm (26 lb-ft).
Flywheel Bolts: 45 Nm (33 lb-ft).
Crankshaft Pulley Bolt: 80 Nm (59 lb-ft).
Camshaft Drive Gear Bolt: 25 Nm (18 lb-ft).
Rocker Arm Shaft Bracket Bolts: 25 Nm (18 lb-ft).
Rocker Arm Adjustment Locknut: 10 Nm (7 lb-ft).
Intake Manifold Bolts: 15 Nm (11 lb-ft).
Exhaust Manifold Nuts: 15 Nm (11 lb-ft).
Injection Pump Mounting Nuts: 15 Nm (11 lb-ft).
Fuel Injection Nozzle Holders: 50 Nm (37 lb-ft).
High-Pressure Fuel Line Nuts: 18 Nm (13 lb-ft).
Glow Plugs: 12 Nm (9 lb-ft).
Water Pump Mounting Bolts (Freshwater): 15 Nm (11 lb-ft).
Seawater Pump Mounting Bolts: 15 Nm (11 lb-ft).
Heat Exchanger Mounting Bolts: 15 Nm (11 lb-ft).
Oil Pan Bolts: 10 Nm (7 lb-ft).
Starter Motor Mounting Bolts: 30 Nm (22 lb-ft).
Alternator Mounting Bolts: 25 Nm (18 lb-ft).
Small Sailboats (Up to 26 ft / 8 m): The 2YM15 is the standard auxiliary
engine for vessels including the Beneteau First 210, Beneteau First 22,
Jeanneau Sun Odyssey 24, and Catalina 250. The low profile allows
installation under cockpit floors.
Daysailers and Pocket Cruisers: Boats such as the Marshall 22 Catboat,
the Cape Dory 25, and the Albin Vega receive the 2YM15 as a replacement
or original power option for inshore and coastal cruising.
Small Commercial Workboats: The engine is used in small fishing skiffs
(under 7 m), harbor launches, and small utility vessels where fuel
economy and compact dimensions are priorities.
KM2P-1 Transmission Configuration: The engine with the 2.62:1 or 3.22:1
reduction gear is used in heavier displacement sailboats requiring a
larger propeller diameter for efficient low-speed thrust.
SD25 Saildrive Configuration: The saildrive version is installed in
yachts with streamlined underwater profiles, including the Beneteau 25.7
and the Jeanneau Sun Odyssey 26. The saildrive reduces engine
compartment noise and simplifies shaft alignment during installation.
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