Volvo Penta MD30A Specifications
| Engine Model: Volvo Penta MD30A |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated freshwater-cooled diesel |
| Total Displacement: 146 cu.in (2.4 L) |
| Rated Engine Power: 65 Hp (48 kW) at 3800 rpm |
| Fuel System Type: Indirect injection |
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The Volvo Penta MD30A is a four-cylinder,
naturally aspirated marine diesel engine from the 30-series family.
Produced throughout the 1980s and early 1990s, this engine serves as the
non-turbocharged variant within the 30-series lineup, known for smooth
operation and high reliability in displacement and semi-displacement
vessels. The MD30A was engineered for marine auxiliary and propulsion
applications, featuring a freshwater cooling system with a heat
exchanger, replaceable wet-type cylinder liners, and a mechanical
indirect injection fuel system. It was offered with multiple drive
configurations including reverse gear, saildrive, and sterndrive
adapters.
The Volvo Penta MD30A embodies a robust naturally aspirated marine
diesel architecture prioritizing durability, serviceability, and smooth
operation. Its inline four-cylinder configuration provides balanced
power delivery suitable for displacement hull cruising. The cast iron
cylinder block with replaceable wet-type cylinder liners permits
in-chassis overhaul, a critical feature for marine applications where
engine removal presents significant labor.
The mechanical indirect injection fuel system, utilizing a Bosch-type
injection pump with a mechanical governor, operates without electronic
controls, facilitating diagnosis and repair in remote marine
environments. The freshwater cooling system with a tubular heat
exchanger isolates the engine block from seawater contact, reducing
internal corrosion. The full pressure lubrication system includes
oil-cooled pistons for improved thermal management under sustained load.
The glow plug system provides cold-start assistance in marine
conditions, with a pre-heat duration appropriate for diesel engine
starting at low ambient temperatures.
Engine Type: Inline 4-cylinder, 4-cycle, freshwater-cooled, naturally
aspirated marine diesel.
Displacement: 2.39 liters (146 cu.in).
Bore x Stroke: 92.0 mm x 90.0 mm (3.62 in x 3.54 in).
Compression Ratio: 21:1.
Firing Order: 1-3-4-2.
Crankshaft Power: 48 kW (65 hp) @ 3,800 rpm.
Propeller Shaft Power: 46 kW (62 hp) @ 3,800 rpm.
Full Throttle Operating Range: 3,700-3,800 rpm.
Idle Speed (In Gear): 700-800 rpm.
Valvetrain: OHV (Overhead Valve), 8 valves (2 valves per cylinder).
Mechanical pushrods and rocker arms. Indirect injection combustion
system.
The cylinder block is constructed from cast iron, providing the
structural rigidity required for sustained marine duty cycles. The block
utilizes replaceable wet-type cylinder liners, each sealed at the lower
flange with rubber O-rings and at the cylinder head interface with a
compression gasket. The wet liner design allows coolant to contact the
outer liner surface directly, delivering superior heat transfer from the
combustion zone.
Five main bearings support the crankshaft. The water jacket surrounds
each liner completely, with cast-in coolant passages. The camshaft is
located within the cylinder block, driven by a gear train from the
crankshaft. The engine mounting points are positioned on the sides and
front of the block, accommodating flexible marine engine mounts for
vibration isolation from the hull structure.
The cylinder head is manufactured from cast iron, selected for its
thermal stability and resistance to distortion under marine diesel
combustion pressures. It employs an OHV configuration with the camshaft
located within the cylinder block. The eight valves are arranged with
two valves per cylinder in a vertical orientation. Valve actuation is
achieved via mechanical pushrods and rocker arms, with screw-and-locknut
adjusters for valve lash setting.
The combustion system is of the indirect injection type, utilizing a
pre-combustion chamber (swirl chamber) for each cylinder. This design
promotes complete combustion across a wide speed range and reduces
combustion noise, a benefit for marine applications. The cylinder head
incorporates separate intake and exhaust ports on opposite sides, with
the intake manifold mounted on the freshwater-cooled side of the engine.
The engine is equipped with a mechanical indirect injection fuel system.
A Bosch-type in-line or distributor-type injection pump is mounted to
the side of the cylinder block, driven by a gear from the camshaft. The
injection pump incorporates a mechanical governor, providing speed
control and load response without electronic input. A manual hand primer
is integrated into the fuel feed pump assembly, allowing fuel system
priming after filter changes without activating the starter motor.
Each cylinder receives fuel from a nozzle-type injector mounted in the
cylinder head, directed into the pre-combustion chamber. The indirect
injection system uses lower injection pressures than direct injection
systems, contributing to quieter operation at the expense of specific
fuel consumption. A fuel filter with water separator is mounted upstream
of the injection pump.
The lubrication system is a full-pressure, wet-sump configuration
designed for marine duty cycles. A gear-type oil pump, driven by the
crankshaft, circulates engine oil through a full-flow disposable spin-on
oil filter. An oil cooler of the seawater-cooled type maintains oil
temperature within operational limits under sustained high-load
operation.
The piston cooling system directs oil jets toward the underside of each
piston crown, managing thermal loads at full throttle conditions. Oil
galleries within the block and cylinder head supply pressurized oil to
the main bearings, connecting rod bearings, camshaft bearings, rocker
arm assemblies, and valve train components. A pressure relief valve
maintains system pressure within specified limits. Total oil capacity is
9.0 liters (9.5 qt).
The cooling system is a thermostat-controlled freshwater (indirect)
cooling design, isolating the engine block from seawater contact. A
belt-driven centrifugal freshwater pump circulates coolant through the
cylinder block, cylinder head, and a tubular heat exchanger. The heat
exchanger transfers heat from the freshwater circuit to the seawater
circuit, which is drawn from the surrounding water body and discharged
overboard.
An integrated expansion tank accommodates coolant expansion and provides
air separation. A seawater pump, separate from the freshwater circuit,
supplies cooling water to the heat exchanger, oil cooler, and exhaust
manifold. A wax-type thermostat, beginning to open at 75-82°C
(167-180°F), regulates freshwater flow to maintain optimal operating
temperatures.
Glow Plug System: The engine is equipped with glow plugs for cold-start
assistance. One glow plug per cylinder is installed in the
pre-combustion chamber, controlled by a push-button or key-switch
circuit. Pre-heat duration of 10-20 seconds is recommended at 0°C
(32°F), with longer pre-heat required at lower temperatures.
Timing System: The camshaft and injection pump are driven by a gear
train housed at the front of the engine. The crankshaft gear drives an
idler gear, which in turn drives the camshaft gear and injection pump
gear. This gear-driven arrangement eliminates timing belt or chain
replacement requirements.
Governor System: The mechanical governor integrated into the injection
pump includes both low-idle and high-speed control functions,
maintaining engine speed under varying propeller load conditions. The
governor is calibrated for marine propeller law characteristics.
Emission Control: No catalytic converter or exhaust gas recirculation
system is present, reflecting the pre-emission era of production. A
crankcase ventilation hose routes blow-by gases to the intake system.
Electrical System: The charging system consists of a 12-volt, two-pole
corrosion-protected alternator rated at 14V/60A. The starter motor is a
12V unit with a solenoid-actuated pinion drive, sized for diesel
cranking requirements. Glow plugs operate on 12V supply.
Dry Weight (Engine Only): 310 kg (683 lb)
Dry Weight (with MS3 Reverse Gear): 360 kg (794 lb)
Dry Weight (with 120S Saildrive): 340 kg (750 lb)
Overall Length (Engine Only): 880 mm (34.6 in)
Overall Width: 520 mm (20.5 in)
Overall Height: 750 mm (29.5 in)
Bore Pitch: 105 mm (4.13 in)
Engine Oil Capacity (with filter): 9.0 liters (9.5 qt).
Engine Oil Specification: SAE 15W-40 or 20W-50 meeting API CD, CE, or
higher.
Engine Oil Pressure (at idle, warm): Minimum 0.8 bar (12 psi).
Engine Oil Pressure (at 3,000 rpm, warm): 3.0-4.5 bar (44-65 psi).
Coolant Capacity (Freshwater Circuit): 6.0 liters (6.3 qt).
Coolant Specification: Ethylene glycol-based antifreeze with corrosion
inhibitors.
Intake Valve Clearance (Cold, Engine stopped): 0.20-0.25 mm (0.008-0.010
in).
Exhaust Valve Clearance (Cold, Engine stopped): 0.25-0.30 mm
(0.010-0.012 in).
Valve Clearance Inspection Interval: Every 500 operating hours.
Fuel Filter Replacement Interval: Every 250 operating hours.
Oil Change Interval: 250 operating hours or annually, whichever occurs
first.
Coolant Change Interval: Every 1,000 operating hours or 2 years.
Idle Speed (In Gear, Engine Warm): 700-800 rpm.
Full Throttle Speed (Loaded): 3,700-3,800 rpm.
Injection Pump Governor Setting: Marine propeller law calibration.
Compression Pressure: Standard: 26-30 bar (377-435 psi) at cranking
speed.
Compression Pressure: Minimum allowable: 22 bar (319 psi).
Compression Pressure: Maximum variation between cylinders: 3 bar (44
psi).
Cylinder Head Bolts, Stage 1: 50 Nm (37 lb-ft).
Cylinder Head Bolts, Stage 2: 100 Nm (74 lb-ft).
Cylinder Head Bolts, Stage 3: 150 Nm (111 lb-ft).
Main Bearing Cap Bolts: 100-110 Nm (74-81 lb-ft).
Connecting Rod Cap Bolts: 60-65 Nm (44-48 lb-ft).
Camshaft Bearing Cap Bolts: 20-25 Nm (15-18 lb-ft).
Flywheel Bolts: 80-85 Nm (59-63 lb-ft).
Crankshaft Pulley Bolt: 200-220 Nm (148-162 lb-ft).
Intake Manifold Nuts: 20-25 Nm (15-18 lb-ft).
Exhaust Manifold Nuts: 25-30 Nm (18-22 lb-ft).
Injector Hold-Down Clamp Bolts: 20-25 Nm (15-18 lb-ft).
Glow Plugs: 15-20 Nm (11-15 lb-ft).
Rocker Arm Shaft Bracket Bolts: 25-30 Nm (18-22 lb-ft).
Valve Cover Nuts: 8-10 Nm (6-7 lb-ft).
Oil Pan Bolts: 15-18 Nm (11-13 lb-ft).
Oil Pump Mounting Bolts: 20-25 Nm (15-18 lb-ft).
Water Pump (Freshwater) Mounting Bolts: 15-20 Nm (11-15 lb-ft).
Seawater Pump Mounting Bolts: 15-20 Nm (11-15 lb-ft).
Injection Pump Mounting Nuts: 30-35 Nm (22-26 lb-ft).
Engine Mount (Bracket to Block): 50-60 Nm (37-44 lb-ft).
The Volvo Penta MD30A engine was utilized across a range of marine
vessels including sailing yachts, motor cruisers, and commercial craft
throughout its production lifecycle.
Sailing Yachts (35-42 Feet): The MD30A was installed as auxiliary
propulsion in displacement cruising sailboats from manufacturers
including Hallberg-Rassy, Najad, Malo, and Sweden Yachts. The engine is
commonly paired with the 120S saildrive unit for reduced vibration and
noise transfer to the hull.
Motor Cruisers (Semi-Displacement): Semi-displacement and displacement
motorboats including the Nimbus 26 and Albin 25 received the MD30A as
factory equipment or as a repower option, providing reliable power for
coastal cruising.
MS3 Reverse Gear Configuration: The engine was offered with the MS3
mechanical reverse gear, featuring a straight or 7° down-angle shaft
output for conventional propeller shaft installations in larger
sailboats and motor vessels.
AQD30A Sterndrive Configuration: When paired with a Volvo Penta 280 or
290 sterndrive, the engine was marketed as the AQD30A, providing
propulsion for planing and semi-planing motorboats up to 25 feet in
length.
Commercial Applications: The MD30A served in small commercial craft
including pilot boats, fishing vessels, and workboats requiring a
naturally aspirated marine diesel with extended service intervals and
parts availability.
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