Volvo Penta MD32A Specifications
| Engine Model: Volvo Penta MD32A |
| Engine Type: 4-cycle inline 6-cylinder naturally aspirated freshwater-cooled diesel |
| Total Displacement: 193 cu.in (3.17 L) |
| Rated Engine Power: 106 Hp (78 kW) at 4000 rpm |
| Fuel System Type: Indirect injection |
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The Volvo Penta MD32A is a 3.17-liter naturally
aspirated inline 6-cylinder marine diesel engine produced between 1970
and 1977. Based on the Peugeot Indenor XDP 6/90 diesel block, this
engine represented the larger displacement sibling to the MD21A within
Volvo Penta’s marine product line. Unlike smaller marine diesels of its
era that utilized 3-cylinder or 4-cylinder configurations, the MD32A’s
6-cylinder architecture delivered exceptional smoothness and reduced
vibration, making it a preferred powerplant for displacement and
semi-displacement hulls where onboard comfort was prioritized.
The engine was offered in multiple configurations: as the MD32A for
shaft drive applications, as the AQD32A when paired with Volvo Penta 270
or 280 sterndrives, and with various Borg Warner or MS reverse gear
transmissions. Its indirect injection system with Ricardo Comet V
combustion chambers and freshwater cooling via heat exchanger
represented the advanced diesel technology of its time.
Engine Family: Volvo Penta MD Series (based on Peugeot Indenor XDP 6/90)
Engine Code: MD32A (also AQD32A for sterndrive version)
Configuration: Inline 6-cylinder, 4-stroke, naturally aspirated diesel,
longitudinally mounted
Displacement: 3168 cc (193 cu.in)
Bore: 90.0 mm (3.543 in)
Stroke: 83.0 mm (3.268 in)
Compression Ratio: 22.2:1
Firing Order: 1-5-3-6-2-4
Valvetrain Configuration: Overhead valve (OHV), 2 per cylinder (12
valves total)
Fuel System: Indirect injection, Ricardo Comet V combustion chambers
Crankshaft Power (Intermittent - Max): 78 kW (106 hp) at 4000 rpm
Continuous Power (Marine Duty): 55 kW (75 hp) at 3000 rpm
Maximum Torque: Not specified in available documentation
Idle Speed: Approximately 600-700 rpm
Aspiration: Naturally aspirated
The cylinder block is a single-piece casting of special-alloy cast iron,
designed to transfer combustion pressure forces from the cylinder head
bolts via reinforced sections directly to the main bearings. The block
incorporates replaceable "wet" cylinder liners, a design feature that
facilitates overhaul without requiring replacement of the entire block.
The wet liner configuration allows coolant to circulate in direct
contact with the external surface of the liners, providing superior heat
dissipation from the combustion zone. The block features a deep-skirt
design with seven main bearings supporting the forged steel crankshaft.
The camshaft bearings are line-bored to the correct dimension after
assembly, ensuring precise alignment. The block incorporates integral
mounting points for the freshwater pump, sea water pump, fuel injection
pump, and the reverse gear housing.
The engine employs two separate cylinder heads, each covering three
cylinders. Each cylinder head is manufactured from special-alloy cast
iron and is attached to the cylinder block with 20 bolts measuring M11
in diameter. The cylinder head gasket is constructed from solid steel
and features sealing grooves formed by two concentric wide grooves sunk
directly into the cylinder head face above the cylinder liner collar.
These grooves adjust the sealing surface area to achieve the required
sealing pressure without the need for excessive tightening torques that
could deform the cylinder liner recess. A separate groove accommodates
the cylinder liner’s flame barrier. Valve seats are pressed into the
head, with exhaust seats receiving stellite facing for high-temperature
durability. Valve clearances are adjustable and are set on the basis of
engine manufacturer specifications.
The fuel system employs indirect injection utilizing Ricardo Comet V
swirl-type combustion chambers, a design that promotes thorough air-fuel
mixing before ignition. A Bosch-type distributor injection pump, driven
by the timing gears, delivers fuel to the injection nozzles at precisely
timed intervals. The pump incorporates a mechanical governor that
maintains consistent engine speed under varying load conditions, a
critical feature for marine propulsion where propeller load changes with
vessel speed and sea state.
A mechanical feed pump supplies fuel from the tank to the injection
pump. The system includes a fuel filter with a replaceable element. Glow
plugs are provided for cold starting assistance, reducing cranking time
in low-temperature conditions. The injection pump timing is adjustable
and must be set precisely using timing marks and a dial indicator.
The lubrication system is a full-pressure wet-sump configuration
utilizing a gear-type oil pump driven from the camshaft. The pump draws
oil through a fixed mesh pickup screen located in the oil pan and
delivers it through a full-flow spin-on oil filter mounted on the
cylinder block. System capacity is 8.5 liters (9.0 qt). Recommended oil
viscosity for normal operating temperatures is SAE 20W-40 or SAE 15W-40
meeting API CC or CD specifications for diesel engines.
Oil pressure at operating speed is maintained within specified ranges.
The system incorporates a pressure relief valve to limit maximum
pressure. The oil pan is designed to maintain oil pickup even when the
vessel is operating at significant angles of heel or trim, a necessary
feature for sailing yacht applications.
The cooling system is a thermostat-controlled freshwater (closed)
cooling configuration utilizing a tubular heat exchanger as standard
equipment. The system comprises two circuits: a freshwater circuit
circulating coolant through the engine block and cylinder heads, and a
raw water circuit drawing seawater through the hull, passing it through
the heat exchanger to absorb heat from the freshwater circuit before
discharging overboard.
A centrifugal freshwater circulation pump is driven by the engine. A
separate rubber-impeller sea water pump supplies raw water for cooling.
An integrated expansion tank accommodates coolant expansion and provides
a filling point. Coolant specified is ethylene glycol-based mixed with
distilled water at appropriate ratio for the expected operating
environment.
Starting System: 12-volt electrical system with a marine-type starter
motor. Glow plugs are provided for cold start pre-heating.
Charging System: Belt-driven marine alternator rated at 35 amperes or 50
amperes depending on vessel electrical load requirements.
Exhaust System: Cast iron exhaust manifold with water injection elbow
where raw water is mixed with exhaust gases to cool the exhaust system.
Reverse Gear Options: Borg Warner Velvet Drive hydraulic transmission
for smooth shifting, MS mechanical reduction gear with various ratios,
or RB reverse gear depending on installation.
Overall Length: 1200 mm (47.2 in)
Overall Width: 600 mm (23.6 in)
Overall Height: 800 mm (31.5 in)
Dry Engine Weight (without reverse gear, coolant, and oil): 355 kg (783
lb)
Fully Dressed Weight (with reverse gear and all accessories): 400-430 kg
(882-948 lb)
Oil Change Interval: 150 operating hours or annually under normal
service.
Oil Filter Replacement: Replace at every oil change interval.
Fuel Filter Replacement: 250 operating hours or as indicated by
restriction.
Primary Fuel Filter (Sedimentor): Inspect and drain water at 100-hour
intervals.
Valve Clearance Adjustment: Inspect every 500 operating hours.
Injection Pump Timing: Verify every 1000 operating hours.
Injection Nozzle Service: Inspect and test every 1000 operating hours.
Coolant Replacement: 1000 operating hours or 24 months.
Heat Exchanger Service: Inspect tubes and clean raw water side every 500
hours.
Rubber Impeller (Sea Water Pump): Inspect every 200 hours; replace
annually.
Drive Belt (Freshwater Pump): Inspect every 250 hours; replace if
cracking.
Glow Plugs: Test resistance at each major service; replace individual
plugs as required.
Sailing Yachts: Hallberg-Rassy 41, Malo models, Baltic Yachts, and other
larger cruising yachts and ketches where low vibration and comfort were
prioritized.
Motor Cruisers: Storebro Royal Cruiser 31, Nimbus 31, and Scandinavian
semi-displacement cruisers.
Fishing Vessels: Small commercial and recreational fishing boats
requiring reliable diesel power.
Sterndrive Configuration (AQD32A): Boats equipped with Volvo Penta 270
or 280 sterndrive units.
Work Boats: Various small commercial marine applications including pilot
boats and harbor craft.
Replacement Installations: The MD32A continues to be found as original
or replacement power in vintage and classic marine vessels.
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