Model Series:
MD marine diesel
Engine Type:
Inline 2-cylinder, 4-stroke marine diesel
Cooling:
Raw water (sea water) cooled
Production Years Covered:
Early 1970s through the mid-1980s
Documentation Scope:
Workshop service and repair procedures for the MD6A and MD7A
Market Position:
Compact marine diesel engines for sailboat auxiliary and small displacement powerboat use
Intended Users:
Boat owners and marine mechanics performing routine service and overhauls
Key Advantage:
Simple mechanical design with easy access to service points makes these engines well-suited to owner maintenance
Key Features:
Direct injection diesel, raw water cooling, mechanical governor, single-lever control compatibility
Design Intent:
Reliable, fuel-efficient propulsion with low maintenance demands
Manual Type:
Downloadable PDF service and repair manual
Format:
PDF (digital download)
Delivery:
Instant download after purchase
Binding:
Digital - no physical binding
Page Count:
N/A - varies by edition of the PDF
Scope:
Engine service, maintenance, disassembly, inspection, and reassembly
Subject Engines:
Volvo Penta MD6A and MD7A marine diesels
Searchability:
Text-searchable PDF for locating procedures quickly
Printing:
Printable for use in the workshop
Engine Mechanical:
Cylinder head, pistons, rings, liners, crankshaft, bearings, and valve train
Lubrication System:
Oil pump, oil filter, galleries, and pressure relief
Cooling System:
Raw water pump, impeller, thermostat, and cooling passages
Fuel System:
Fuel lift pump, injection pump, injectors, and fuel filtration
Exhaust System:
Exhaust manifold, elbow, and water injection into the exhaust
Electrical System:
Battery, charging, starting, and engine wiring
Starting System:
Starter motor service and inspection
Charging System:
Alternator service and drive belt adjustment
Governor:
Mechanical governor adjustments and linkages
Diagnosis:
Troubleshooting charts for starting, running, and performance faults
Disassembly:
Step-by-step engine teardown in logical order
Inspection:
Measurement and wear limit checks on internal components
Reassembly:
Torque sequences and clearances for rebuilding the engine
Adjustment:
Valve clearances, injection timing, and governor settings
Maintenance:
Routine service tasks and seasonal lay-up procedures
Measurement Specifications:
Component wear limits and service tolerances
Torque Values:
Fastener torque figures for critical assemblies
Line Drawings:
Illustrations and cutaway diagrams supporting procedures
Part Identification:
Component naming and location for service reference
Component Reference:
Parts identified by assembly and function for ordering and inspection
Wear Items:
Filters, impellers, belts, gaskets, and seals listed for service
Spare Parts:
Commonly replaced items noted for stock planning
File Format:
PDF (searchable, bookmarked, zoomable)
Compatibility:
Windows, macOS, Linux, iOS, and Android — any device with a PDF reader
Requirements:
A PDF reader application (e.g. Adobe Acrobat Reader, free)
Searchability:
Fully text searchable for fast lookup of any topic
Print Quality:
High-resolution digital pages, printable at full clarity
Binding Type:
N/A — digital download, no physical binding
Paper Type:
N/A — digital download, no physical paper
Primary Engine:
Volvo Penta MD6A - 2-cylinder marine diesel
Engine Options:
MD6A (smaller output) and MD7A (higher output)
Configuration:
Inline 2-cylinder, 4-stroke, direct injection diesel
Cooling:
Raw water (indirect underway) cooled
Displacement:
N/A - not published in this manual edition
Power Output:
N/A - factory output varies by rating and propeller load
Rated Speed:
N/A - refer to engine plate for specific rating
Fuel Type:
Marine diesel fuel oil
Fuel System:
Mechanical inline injection pump with lift pump and injectors
Governor:
Mechanical centrifugal governor
Standard Transmission:
Marine reduction/reversing gearbox matched to engine
Optional Transmission:
Various marine gearboxes offered with the MD6A/MD7A
Control:
Mechanical throttle and gear selection via single-lever control
Output:
Reversing reduction gear to propeller shaft
Coupling:
Flexible coupling to propeller shaft
Lubrication:
Gearbox oil as specified by the gearbox manufacturer
Engine Type:
Marine diesel, compact 2-cylinder block
Length:
N/A - varies with gearbox and accessory fitment
Width:
N/A - varies with accessory fitment
Height:
N/A - varies with accessory fitment
Dry Weight:
N/A - depends on engine and gearbox combination
Installed Weight:
N/A - confirm against vessel installation documentation
Overheat Protection:
Raw water cooling with temperature monitoring provisions
Oil Pressure:
Oil pressure warning provisions
Shutdown Provisions:
N/A - optional on some installations, not integral to base engine
Crash Ratings:
N/A - applies to vessels, not a marine engine
Fuel Delivery:
Mechanical direct injection with lift pump and injectors
Governor:
Mechanical speed governing
Cooling:
Raw water pump and thermostat-controlled circuit
Electrical:
Battery charging and electric starting
Instrumentation:
N/A - depends on vessel instrument panel
Break-In Service:
Initial oil and filter change per engine commissioning schedule
Routine Service:
Regular oil, filter, and impeller inspection
Lay-Up Service:
Seasonal preservation and recommissioning procedures
Fuel System:
Filter changes and water drain intervals
Cooling System:
Impeller replacement and cooling circuit flushing
Engine Oil:
N/A - use viscosity and grade recommended for the operating climate in the manual
Coolant:
Raw water cooling - no coolant mix specified
Fuel:
Marine diesel fuel oil
Gearbox Oil:
Per gearbox manufacturer specification
Impeller:
Raw water pump impeller wears and requires periodic replacement
Filters:
Oil and fuel filters are routine service items
Belts:
Alternator drive belt requires tension checks and periodic replacement
Seals and Gaskets:
Inspect for leaks during service
Exhaust Elbow:
Inspect for corrosion and blockage
Manufacturer:
Volvo Penta
Origin:
Volvo Penta, derived from the Volvo Group marine engine business
Reputation:
Known for durable, simple marine diesel engines
Placement:
MD6A and MD7A served the small auxiliary diesel market
Design:
Mechanically governed, raw water cooled direct injection diesel
Legacy:
Widely used in sailboats for auxiliary propulsion
Country:
N/A - confirm against engine identification plate
