Volvo Penta MD11D Specifications
| Engine Model: Volvo Penta MD11D |
| Engine Type: 4-cycle 2-cylinder naturally aspirated freshwater-cooled diesel |
| Total Displacement: 68 cu.in (1.12 L) |
| Rated Engine Power: 25 Hp (18.4 kW) at 3000 rpm |
| Fuel System Type: Direct injection |
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The Volvo Penta MD11D is a two-cylinder,
naturally aspirated marine diesel engine produced by Volvo Penta as an
evolution of the earlier MD11C power unit. This engine was specifically
engineered for sailboats and small displacement motorboats requiring
reliable, low-speed propulsion with extended service intervals.
The MD11D introduced freshwater cooling with a heat exchanger as
standard equipment, distinguishing it from prior seawater-cooled
variants. A heavy flywheel characterises the engine, providing smooth
running at low rotational speeds between 700 rpm and 3000 rpm. The
engine is offered with either a mechanical reverse gear (MSB) or a
saildrive unit (110S or 120S) for direct mounting to a sailboat's hull.
The Volvo Penta MD11D is a water-cooled, 4-stroke, inline 2-cylinder
naturally aspirated diesel engine. It operates on a direct injection
fuel system with a mechanical governor. The engine features a cast iron
cylinder block with individual cylinder heads for each cylinder. The
valvetrain is an overhead valve (OHV) pushrod design with 2 valves per
cylinder, totalling 4 valves. Lubrication is a full-pressure system with
a spin-on full-flow oil filter. Cooling is provided by a freshwater
closed-loop circuit with a heat exchanger and a belt-driven seawater
pump for the raw water side. The electrical system is 12 V, equipped
with a marine alternator rated at 35 A or 50 A.
Engine Type: Inline 2-cylinder, 4-stroke, naturally aspirated diesel
Displacement: 1.12 L (68 cu.in)
Bore: 88.9 mm (3.50 in)
Stroke: 90.0 mm (3.54 in)
Compression Ratio: 17:1
Crankshaft Power: 18.4 kW (25 hp) at 3000 rpm
Idle Speed: 700 rpm to 800 rpm
Firing Order: 1-2
Aspiration: Naturally aspirated
Combustion System: Direct injection
Fuel System: Bosch-type inline injection pump with mechanical governor
Valvetrain: OHV (pushrod), 4 valves (2 per cylinder)
Valve Clearance (cold): Intake 0.30 mm (0.012 in); Exhaust 0.30 mm
(0.012 in)
Electrical System: 12V
Alternator Output: 35A or 50A (depending on specification)
The cylinder block is constructed from grey cast iron with a deep-skirt
design, providing rigidity and damping of torsional vibrations generated
during low-speed, high-torque operation. The block is a monobloc casting
with integral water jackets surrounding the two cylinders. Unlike wet
liner designs, the MD11D block uses parent bore cylinders machined
directly into the cast iron material.
The cylinder bores are induction-hardened and honed to a plateau finish
for oil retention. The block houses two main bearings, with the thrust
bearing located at the rear main bearing position. The timing gear
housing is cast integrally into the front of the block. A side-mounted
mechanical fuel feed pump with a manual primer lever is bolted directly
to the block face. The oil filler neck and dipstick tube are integrated
into the block structure.
Crankshaft: Forged from carbon steel with three main bearing journals
(front, center, rear). The crankshaft incorporates two integral
counterweights positioned opposite each crank throw. A heavy flywheel is
bolted to the rear flange; this flywheel has a significantly larger mass
than automotive equivalents to maintain rotational inertia during firing
intervals between the two cylinders.
Connecting Rods: Forged steel, I-beam cross-section. The rod and cap are
machined as a matched set. The piston pin end is bushless with a fully
floating piston pin retained by circlips.
Pistons: Cast aluminum alloy with a shallow combustion bowl. Three
piston rings: two compression rings (top ring chromed) and one oil
control ring with an expander. Piston cooling is achieved by splash and
oil mist; no dedicated oil jets are fitted.
The engine employs two individual cylinder heads, one for each cylinder,
rather than a single common head. Each head is a separate casting
manufactured from alloyed cast iron. This design simplifies servicing
and gasket repair. Each cylinder head contains two valves: one intake
and one exhaust. The valves are arranged in-line along the cylinder
axis. The combustion chamber is formed as a pre-combustion swirl chamber
within the head, promoting complete combustion of the direct-injected
fuel.
Valve seats are induction-hardened directly into the head material.
Valve guides are press-fit cast iron sleeves. The OHV valvetrain is
actuated by a camshaft located in the cylinder block, operating pushrods
that transfer motion to rocker arms mounted on a shaft above each
cylinder head. Rocker arms have threaded adjusters and locknuts for
valve lash setting.
The fuel system is a mechanically governed direct injection design. A
Bosch-type inline injection pump, mounted to the side of the cylinder
block, is driven by the engine timing gears. The pump contains one
plunger and barrel per cylinder. A mechanical centrifugal governor
integrates with the injection pump to maintain selected engine speed
under varying load.
A separate fuel feed pump (diaphragm type) with a built-in manual primer
lever draws fuel from the tank and supplies it to the injection pump
through a primary fuel filter. High-pressure injection lines of equal
length connect the pump to the injectors. Each injector is a pintle-type
nozzle set to a cracking pressure of 12.0 MPa to 12.5 MPa (1740 psi to
1810 psi). Excess fuel from the injectors returns to the fuel tank via a
leak-off line.
The lubrication system is a full-pressure, wet-sump design. A gear-type
oil pump is mounted inside the timing gear cover and driven directly
from the crankshaft gear. The pump draws oil through a strainer pickup
tube submerged in the stamped steel oil pan. Oil passes through a
full-flow spin-on filter mounted externally on the block.
A pressure relief valve, integral to the filter mount or oil pump,
maintains system pressure between 200 kPa and 350 kPa (29 psi to 51 psi)
at operating speed. Oil galleries drilled within the cylinder block
supply the main bearings, camshaft bearings, and the rocker arm shaft
via an external pipe. The oil pan capacity is 2.9 L (3.1 qt) including
the filter. An oil dipstick is located on the side of the block. No oil
cooler is fitted in standard configuration.
The MD11D features a dual-circuit cooling system with freshwater
closed-loop cooling as standard. The internal circuit circulates a
mixture of antifreeze and corrosion inhibitor through the cylinder
block, cylinder heads, and a tubular heat exchanger. A belt-driven
centrifugal fresh water pump circulates the internal coolant. A
wax-pellet thermostat located in the freshwater outlet housing begins
opening at 82°C (180°F) and achieves full lift at 95°C (203°F).
The external raw water circuit, drawn from the surrounding body of
water, is circulated by a flexible-impeller pump (seawater pump) also
driven by the front belt. Raw water passes through the heat exchanger
tubes, absorbing heat from the fresh water before exiting through the
exhaust elbow. The heat exchanger is a shell-and-tube design with
removable end caps for cleaning. Coolant capacity of the fresh water
circuit is 2.0 L to 2.5 L (2.1 qt to 2.6 qt).
Timing Drive: All auxiliary drives (camshaft, injection pump, oil pump)
are driven by spur gears housed in the front timing case. The crankshaft
gear drives an intermediate idler gear, which in turn drives the
camshaft gear and the injection pump gear. No timing chain or belt is
used.
Exhaust System: A cast iron exhaust manifold collects gases from both
cylinders. Raw water is injected into the manifold at the exhaust elbow
to cool the exhaust gases before discharge below the waterline.
Mounting System: The engine is supported by four flexible rubber mounts
attached to brackets on the cylinder block. The MSB reverse gear or
110S/120S saildrive unit bolts directly to the flywheel housing.
Starting System: A 12 V electric starter motor is mounted on the
flywheel housing, engaging a ring gear on the flywheel. Manual starting
via a hand crank is provided as an emergency option.
Length (excluding gearbox): 760 mm (29.9 in) from crankshaft pulley to
flywheel housing.
Length (with MSB gearbox): 890 mm (35.0 in).
Width (at engine mounts): 470 mm (18.5 in).
Height (from oil pan to rocker cover): 590 mm (23.2 in).
Dry Weight (without gearbox or fluids): 200 kg (441 lb).
Dry Weight (with MSB reverse gear): 230 kg (507 lb).
Dry Weight (with 110S saildrive): 250 kg (551 lb).
Engine Oil Capacity (with filter): 2.9 L (3.1 qt).
Recommended Oil Grade: SAE 15W-40 or 20W-50 meeting API CC, CD, or CE.
Coolant Capacity (freshwater circuit only): 2.3 L (2.4 qt).
Raw Water Pump Impeller Replacement Interval: Annually or 200 hours.
Valve Clearance Adjustment Interval: 500 hours.
Oil Change Interval (normal service): 200 hours or annually.
Fuel Filter (primary) Replacement Interval: 200 hours.
Oil Filter Replacement Interval: 200 hours (at each oil change).
Injector Nozzle Inspection Interval: 1000 hours.
Idle Speed Adjustment: 700 rpm to 800 rpm in neutral.
Compression Pressure (minimum): 2.2 MPa (320 psi) at cranking speed.
Thermostat Opening Temperature: 82°C (180°F).
Cylinder Head Bolts (M12), Stage 1: 30 Nm (22 lb-ft)
Cylinder Head Bolts (M12), Stage 2: 60 Nm (44 lb-ft)
Cylinder Head Bolts (M12), Stage 3: 110 Nm (81 lb-ft)
Main Bearing Cap Bolts: 80 Nm (59 lb-ft)
Connecting Rod Cap Bolts: 50 Nm (37 lb-ft)
Crankshaft Pulley Bolt (center): 150 Nm (111 lb-ft)
Flywheel Bolts (to crankshaft): 60 Nm (44 lb-ft) + 60° angle
Rocker Arm Shaft Bracket Nuts: 25 Nm (18 lb-ft)
Rocker Arm Adjuster Locknut: 15 Nm (11 lb-ft)
Injection Pump Mounting Nuts: 25 Nm (18 lb-ft)
Injector Clamp Bolt: 25 Nm (18 lb-ft)
Intake Manifold Bolts: 20 Nm (15 lb-ft)
Exhaust Manifold Nuts: 30 Nm (22 lb-ft)
Oil Pan Bolts: 15 Nm (11 lb-ft)
Heat Exchanger Mounting Bolts: 20 Nm (15 lb-ft)
Starter Motor Mounting Bolts: 35 Nm (26 lb-ft)
Engine Mount Bracket to Block Bolts: 45 Nm (33 lb-ft)
MSB Reverse Gear Mounting Bolts (to flywheel housing): 40 Nm (30 lb-ft)
The Volvo Penta MD11D was installed as auxiliary propulsion in sailboats
and small motor cruisers between approximately 1978 and 1990.
Sailboats (28 ft to 34 ft):
Hallberg-Rassy 312.
Westerly Konsort.
Bavaria 30 and 32.
Najad 320.
Scanmar 33.
Malo 32.
Moody 31.
Motor Cruisers:
Small displacement semi-displacement hulls up to 8 m (26 ft).
Traditional Swedish "Snipa" motor launches.
Drive Configurations:
MSB Mechanical Reverse Gear: Direct shaft drive with either straight
(0°) or 7° down-angle output flange.
110S Saildrive: 1.66:1 reduction ratio, integrated with a lower drive
leg passing through the hull.
120S Saildrive: 2.00:1 reduction ratio, designed for heavier
displacement sailboats.
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