Volvo Penta MD 2020 Specifications
| Engine Model: Volvo Penta MD 2020 |
| Engine Type: 4-cycle inline 3-cylinder naturally aspirated freshwater-cooled diesel |
| Total Displacement: 41.5 cu.in (0.68 L) |
| Rated Engine Power: 19 Hp (13.8 kW) at 3600 rpm |
| Fuel System Type: Indirect injection |
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The Volvo Penta MD2020 is a three-cylinder,
naturally aspirated marine diesel engine produced from the late 1980s
through the early 2000s. Developed in collaboration with Perkins as part
of the 2000-series, this power unit was engineered specifically for
small to mid-sized displacement sailboats where space, weight, and
reliability are paramount. The MD 2020 is distinguished by its compact
inline-three configuration, cast iron construction, and freshwater
cooling system with a heat exchanger - a feature that prevents internal
seawater corrosion and allows connection to a cabin water heater
(calorifier).
The engine is offered with either a mechanical reverse gear (MS2) for
shaft drive or a 120S saildrive for direct propeller mounting, the
latter becoming extremely popular in sailing yachts for reduced
vibration and simplified installation. With a power output of 19
crankshaft horsepower and a dry weight as low as 116 kg, the MD2020
established itself as a gold standard for yachts ranging from 28 to 34
feet, powering vessels from Beneteau, Jeanneau, Bavaria, and Westerly
among many others.
The Volvo Penta MD 2020 is a four-stroke, water-cooled, inline-three
diesel engine with a total displacement of 0.68 L (41.5 cu.in). The bore
and stroke dimensions are 67 mm (2.64 in) and 64 mm (2.52 in),
respectively, creating a slightly oversquare configuration that favors
smooth operation and moderate-rpm power delivery. The valvetrain employs
an overhead valve (OHV) design with two valves per cylinder for a total
of six valves. The camshaft is positioned within the cylinder block and
actuates the valves through pushrods and rocker arms.
The fuel system is an indirect injection design utilizing a
flange-mounted in-line injection pump with a mechanical governor.
Induction is naturally aspirated through a cast iron intake manifold.
The combustion system incorporates a pre-combustion chamber for smooth,
quiet operation characteristic of marine auxiliary diesels.
The compression ratio is set at 23.5:1, a high value that provides
reliable cold-start performance and efficient combustion at the low
engine speeds common in sailboat propulsion. Idle speed is maintained at
850 rpm ± 25 rpm. Crankshaft power is rated at 13.8 kW (19 hp) at 3,600
rpm. Propeller shaft power, accounting for transmission losses, is 13 kW
(18 hp). The engine speed range for continuous operation is 800 to 3,600
rpm. The firing order is 1-2-3, the standard arrangement for
inline-three engines.
The cylinder block is constructed from cast iron, a material selected
for its exceptional rigidity, acoustic damping properties, and
resistance to thermal distortion under sustained marine operating
conditions. The block utilizes a tunnel-type crankcase design, where the
crankshaft runs in a continuous tunnel of bearing shells rather than
individual bearing caps. This design provides high rigidity and superior
crankshaft alignment. The inline-three configuration incorporates four
main bearings supporting a forged steel crankshaft.
Cylinder liners are integrated directly into the block casting rather
than being replaceable inserts. The bores are precision-machined and
finished with a plateau honed process to optimize oil retention and
piston ring sealing. The water jacket surrounds the cylinders for
effective heat transfer, with coolant flow directed upward toward the
cylinder head. The block is designed with an inclined mounting angle in
saildrive installations, with the rear of the engine lower than the
front to accommodate the 120S saildrive unit. Cast-in mounting feet with
resilient rubber mounts reduce vibration transmission to the hull.
The cylinder head is manufactured from cast iron, matching the thermal
expansion characteristics of the block to ensure consistent head gasket
sealing. The overhead valve (OHV) arrangement positions the camshaft
within the block, with valve actuation provided by pushrods and rocker
arms. The rocker arms pivot on a rocker shaft mounted to the cylinder
head and are adjustable to set valve clearance.
Valves are arranged in-line along the cylinder head axis, with each
cylinder served by one intake valve and one exhaust valve. The indirect
injection system incorporates a pre-combustion chamber for each
cylinder, machined into the cylinder head. This pre-chamber design slows
the initial pressure rise during combustion, resulting in quieter
operation and reduced mechanical stress on the rotating assembly.
Valve seat inserts are pressed into the cylinder head and machined to
precise angles to ensure proper sealing under diesel combustion
pressures. The valve springs are of the single-coil type. The cylinder
head gasket is a composite or multi-layer steel design, providing
reliable sealing between the cast iron head and cast iron block.
The fuel system is a mechanical indirect injection system utilizing a
flange-mounted in-line injection pump. The pump is mounted directly to
the cylinder block and driven by the camshaft, ensuring precise
synchronization. Each cylinder has its own pump element (plunger and
barrel), delivering high-pressure fuel through steel lines to the
injection nozzles. A mechanical governor integrated into the injection
pump maintains engine speed under varying propeller loads, automatically
adjusting fuel delivery to hold the set speed.
The injection nozzles are of the pintle type, positioned within each
pre-combustion chamber. A feed pump, mounted to the injection pump,
draws fuel from the marine fuel tank through a water-separating primary
filter and a secondary fine filter. A manual primer lever on the feed
pump allows bleeding of air from the system after filter replacement, a
critical feature for marine applications where fuel system maintenance
may occur away from workshops.
The indirect injection system provides smoother idle and quieter
operation than direct injection diesels, though at a small penalty in
specific fuel consumption. The governed speed range is matched to
typical sailboat propeller curves, with the governor providing droop to
prevent over-speeding in following seas.
The lubrication system is a full-pressure, full-flow circuit utilizing a
gear-type oil pump mounted within the timing gear case. The pump draws
engine oil from a cast aluminum sump through a strainer screen before
directing it through a spin-on full-flow oil filter. An oil pressure
relief valve maintains system pressure within the specified range.
The main oil gallery distributes pressurized oil to the crankshaft main
bearings, connecting rod bearings, camshaft bearings, and rocker arm
assemblies. The timing gears are lubricated by splash oil. The total
engine oil capacity, including the filter, is 2.8 L (3.0 qt).
Recommended oil viscosity is SAE 15W-40 or 10W-30 for moderate climates,
with diesel-rated API classifications such as CC, CD, or CF. SAE 30
mono-grade oil is acceptable in warm ambient temperatures.
The cooling system is a thermostatically controlled freshwater (closed)
cooling circuit with a heat exchanger. This design isolates the engine
block and cylinder head from seawater, preventing internal corrosion and
allowing the use of conventional automotive antifreeze. A belt-driven
centrifugal water pump circulates freshwater through the cylinder block,
cylinder head, and the tube stack of the heat exchanger. A separate
seawater pump, of the flexible-impeller type, draws raw water through a
through-hull fitting and strainer, circulates it through the shell side
of the heat exchanger, and then discharges it with the exhaust gases
through the water-injected exhaust elbow.
The thermostat is a wax-pellet type positioned on the freshwater coolant
outlet, maintaining engine temperature within the range of 80°C to 90°C
(176°F to 194°F). The heat exchanger is constructed with a cupronickel
tube stack for seawater corrosion resistance. An expansion tank allows
for coolant expansion and provides a point for air separation. The
freshwater cooling circuit includes outlets for connection to a cabin
water heater (calorifier), using engine waste heat for domestic hot
water. The total freshwater capacity is 4.0 L (4.2 qt). Seawater flow
requirements vary with engine speed.
| Intake and Exhaust Systems |
Intake System: The intake manifold is constructed from cast iron. The
naturally aspirated induction system draws air through a dry-type paper
air filter housed in a plastic air cleaner assembly with a flame
arrestor for marine safety compliance. An intake silencer reduces
induction noise in enclosed engine compartments.
Exhaust System: The exhaust manifold is constructed from cast iron. The
water-injected exhaust elbow mixes seawater from the cooling system with
exhaust gases, cooling the exhaust to safe temperatures for rubber
exhaust hoses and preventing heat damage to the fiberglass hull. A
waterlock (gooseneck) prevents seawater from flowing back into the
engine through the exhaust system. Exhaust back pressure must be
maintained within specified limits for proper engine operation.
The electrical system operates on 12 volts with a 60-amp marine
alternator and an integrated charging regulator. The alternator is
designed to provide adequate charging current for starting batteries and
house batteries in sailboat applications. A single or dual battery bank
arrangement is supported. The starter motor is a high-torque,
pre-engaged type designed for marine environments with
corrosion-resistant coatings.
Timing Drive: The camshaft and injection pump are driven by a gear train
from the crankshaft. This gear drive system eliminates the need for
timing belt or chain replacements and contributes to the engine’s long
service life in marine applications. Accessory drives for the freshwater
pump and alternator are belt-driven from the crankshaft pulley.
Reverse Gear / Saildrive Options: The MD 2020 is offered with two
transmission configurations. The MS2 reverse gear is a mechanical
transmission providing forward, neutral, and reverse gears, available
with straight or 7-degree down-angle output for conventional shaft
drive. The 120S saildrive is a lower-mounted unit that passes through a
sealing diaphragm in the hull, combining a 2:1 reduction gear with a
vertically oriented propeller shaft. The saildrive reduces vibration,
improves hull efficiency, and simplifies alignment.
The overall length, measured from the front accessory drive to the
flywheel housing face with MS2 gear, is 680 mm (26.8 in). Width across
the cylinder head and heat exchanger is 500 mm (19.7 in). Height from
the bottom of the oil sump to the top of the heat exchanger is 560 mm
(22.0 in). The dry weight varies by configuration: MS2 reverse gear
version is 116 kg (256 lb); 120S saildrive version is 144 kg (317 lb).
The MD2020 requires structured maintenance aligned with marine service
intervals. The engine oil and filter must be replaced after the first 50
hours of operation, then every 100 operating hours or annually,
whichever comes first. The oil capacity is 2.8 L (3.0 qt). The fuel
filter and water separator require replacement every 200 operating hours
or as indicated by reduced engine performance.
The seawater pump impeller requires inspection annually and replacement
every 200 to 500 operating hours depending on operating conditions. The
heat exchanger tube stack should be removed and cleaned every 500
operating hours or whenever seawater flow is reduced. Valve clearance
adjustment is required at intervals of 500 operating hours, with cold
clearances specified in the service manual.
The freshwater coolant requires replacement every two years. The anodes
in the seawater cooling circuit must be inspected annually and replaced
when 50% consumed. The saildrive diaphragm (for 120S versions) requires
inspection every two years and replacement every seven years regardless
of condition.
0Cylinder Head Bolts, Stage one: 30 Nm (22 lb-ft).
Cylinder Head Bolts, Stage two: 60 Nm (44 lb-ft).
Main Bearing Cap Bolts: 70 Nm (52 lb-ft).
Connecting Rod Cap Bolts: 35 Nm (26 lb-ft).
Rocker Arm Shaft Bracket Bolts: 25 Nm (18 lb-ft).
Flywheel Bolts: 50 Nm (37 lb-ft).
Crankshaft Pulley Bolt: 100 Nm (74 lb-ft).
Intake Manifold Bolts: 20 Nm (15 lb-ft).
Exhaust Manifold Nuts: 25 Nm (18 lb-ft).
Injection Pump Mounting Nuts: 25 Nm (18 lb-ft).
Injector Holders: 70 Nm (52 lb-ft).
Oil Pan Bolts: 12 Nm (9 lb-ft).
The Volvo Penta MD2020 engine was deployed almost exclusively in
sailboats and small displacement cruisers, with no automotive
applications.
Beneteau Oceanis Series (28 to 34 feet): The MD2020 was a standard
engine in various Beneteau Oceanis models, including the Oceanis 311,
323, 331, and 34, providing reliable auxiliary power for coastal and
offshore cruising.
Jeanneau Sun Odyssey Series (29 to 34 feet): The engine powered numerous
Sun Odyssey models, including the 29.2, 32.1, 32.2, 34, and 34.2, where
its compact dimensions fit within the aft berth engine compartment.
Bavaria Yachts (30 to 34 feet): Bavaria equipped many of its popular
cruising yachts, including the Bavaria 30, 32, 34, and 34 Cruiser, with
the MD2020, often paired with the 120S saildrive.
Westerly Yachts: The MD2020 was installed as a replacement engine in
several Westerly models and occasionally as original equipment in later
Westerly production.
Sweden Yachts: The Sweden Yachts 36 and other models used the MD2020 for
auxiliary power.
Moody Yachts: Several Moody models, including the Moody 31 and 346,
utilized the MD2020.
Canal and River Cruisers: The engine was also installed in small inland
waterways cruisers and narrowboats where its low vibration and quiet
operation were advantageous. The MD2020 remains widely available as a
replacement engine for older yachts originally powered by the MD11C,
MD17C, or other small marine diesels.
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