Volvo Penta · Inboard diesel

Volvo Penta MD7A

The MD7A is a small two-cylinder Volvo Penta diesel with direct injection and direct raw-water cooling, fitted as an auxiliary in sailing yachts of the late 1970s and early 1980s. It gives 9.6 kW (13 hp) at 2600 rpm and came with the MS-B reverse gear or on the 110S saildrive. Its successor, the MD7B (operator’s manual dated 1981), keeps the same 0.744-litre block but gives 12.5 kW (17 hp) at 3000 rpm and was paired with the MS2 reverse gear or the 120S saildrive; this page covers both, and the notes say where belts, drives or anodes differ. The smaller MD6A/MD6B (0.631 l, 10 hp) came before them and shares the impeller kit, the oil and fuel filters and the thermostat; the MD2010/MD2020 generation followed.

Manuals & documents
Wear parts & part numbers
Service intervals
Specifications
Good to know
Fitted in
On the marketplace

Manuals & documents

The links go straight to Volvo Penta. We host no manuals or drawings — the manufacturer’s copy is the current one.

Instruction book MD7A, MD7A/110S (1980, scan) Operation manual pubs.volvopenta.com · PDF · EN
Operator’s manual MD7B/MS2, MD7B/120S (1981, multilingual, scan) Operation manual pubs.volvopenta.com · PDF · EN
Instruction book MD6A/MD6B (predecessor, scan) Operation manual pubs.volvopenta.com · PDF · EN
Product bulletin MD7A with MS-B reverse gear Spec sheet pubs.volvopenta.com · PDF · EN
Product bulletin MD7A/110S saildrive Spec sheet pubs.volvopenta.com · PDF · EN
Product leaflet MD7B/MS2 and MD7B/120S Product leaflet pubs.volvopenta.com · PDF · EN
Volvo Penta manuals & handbooks: MD7A Manual portal volvopenta.com · EN
Volvo Penta manuals & handbooks: MD7B Manual portal volvopenta.com · EN
Volvo Penta parts catalogue, filtered to MD7A (shared with MD7B) Parts catalogue volvopenta.com · EN
Parts catalogue: raw water pump 840076 (MD7A, MD7B) Parts catalogue volvopenta.com · EN

Wear parts & part numbers

Part	OEM number	Also fits	Note
Impeller kit (with gasket)	`21951342`^1,2,3replaces 3586496	—	MD7A and MD7B; Volvo Penta also lists it for the MD6A. The kit includes the pump cover gasket. Older on-board kits (875642) contain the earlier impeller kit 875583, which Volvo no longer prices.
Pump cover gasket	`833994`^1,4	—	MD6A, MD6B, MD7A and MD7B; also part of the impeller kit.
Raw water pump	`858065`^1,5,6replaces 840076	—	Replaces the original pump 840076 on the MD7A and MD7B.
Water pump repair kit	`21951422`^1,7	—	Shaft kit for pump 858065: shaft, seals, two bearings and circlip.
Engine oil filter	`834337`^8,9,10	—	Spin-on filter for MD6A, MD6B, MD7A and MD7B. Volvo Penta’s shop still lists the number but shows no price.
Fuel filter (engine)	`829913`^11,12,13	—	Throw-away element for filter housing 840531, fitted from engine no. 33080 and the service replacement for the earlier housing 829992. Check your housing first (next row); the very first MD6/MD7A housing 3875693 took element 243464.
Fuel filter (engine)	`829993`^14,15,16	—	Only for the earlier housing 829992 (MD6A to MD7B up to engine no. 33079). Volvo Penta no longer shows a price for it.
Fuel pre-filter	`829666`^17,18	—	Insert for Volvo Penta’s optional water separator 833971; only if that separator is fitted.
Fuel lift pump	`834255`^19,20,15	—	Repair kit with strainer for feed pump 833323 (with hand primer), not the complete pump. MD6A, MD6B, MD7A and MD7B.
Air filter	`833414`^21,22,23	—	Air filter and intake silencer in one, for MD6A to MD7B. The element is washable, not a throw-away part.
Alternator V-belt	`958327`^24,25,3	—	MD7A (also MD6A/MD6B), 1425 mm long.
Alternator V-belt	`958328`^26,27	—	MD7B only (different alternator and pulley), 1450 mm long.
Thermostat	`875796`^21,22,28	—	Thermostat kit, 60 °C; MD6A, MD6B, MD7A and MD7B.
Thermostat gasket	`416033`^21,19,29	—	Sealing ring used from engine no. 28014 (it replaced the earlier seal); also in the decarbonising kit 876431.
Exhaust mixing elbow	`833998`^30,31,32	—	Water-cooled elbow on the MD7B and later MD7A (from engine no. 27023, specifications 867418/-496/-497). Earlier MD7A have assembly 829539, which contains the same elbow.
Exhaust elbow gasket	`800326`^30,33	—	MD6A, MD6B, MD7A and MD7B.
Fuel injector	`838289`^15,34,35replaces 838153	—	Two per engine. Fitted from engine no. 28771 and replaces the earlier 838153. Nozzle: 838287.
Cylinder head gasket	`3809167`^19,36	—	MD7A and MD7B; also in the decarbonising kit 876431.
Gasket set	`876431`^19,37	—	Decarbonising (top-end) kit for MD7A and MD7B: seals for head, rocker cover, manifold, injectors and thermostat. The full overhaul set 875509 is no longer priced.
Valve cover gasket	`840115`^38,39,40replaces 3875384	—	Rocker cover gasket, MD6A, MD6B, MD7A and MD7B.
Saildrive anode	`875812`^41,42,43	—	Zinc anode for the 110S saildrive (MD7A) in salt water; the magnesium version for fresh water is 876603.
Saildrive anode	`851983`^44,45,46	—	Zinc ring for the 120S saildrive (MD7B). Volvo Penta lists it without a price; one dealer supplies zinc ring kit 876286 as the same anode for the 120 drives.
Propeller anode	`833913` · `833915` · `828140`^47,48,49,50	—	Shaft installations only: zinc anode on the propeller shaft, 833913 for 25 and 30 mm shafts, 833915 for 35 mm, 828140 for 40 and 45 mm.
Vented loop	`828534`^21,22,51replaces 828263	—	Volvo Penta vacuum valve (anti-siphon) in the cooling-water line; it holds two diaphragms 828264 and gaskets 828424.
Gasket set	`875704`^52,53,54	—	Gasket kit for the MS2 reverse gear (MD7B); MS2 gears 851610 (2.37:1) and 851611 (3.02:1).
Gasket set	`875591` · `875720`^55,56	—	Saildrive gasket and locking kit: 875591 for the 110S (MD7A), 875720 for the 120S (MD7B).
Engine mount	`850402`^57,58,59,60	—	Saildrive installations (MD7A/110S, MD7B/120S): the two front rubber elements. The single rear element 850404 is replaced by rubber element 840845 plus stud 924075.
Engine mount	`833950`^61,62	—	Shaft installations with reverse gear (not the COMBI versions): four rubber cushions.

Numbers checked against the sources below on 12 October 2026. Always confirm against your serial number and exact type before ordering.

Service intervals

Task	Interval
First service	New or overhauled engine: retighten the cylinder head nuts after the first 20 h, then check the valve clearance⁶³
Engine oil change	Every 50 h, first time after 20 h⁶³
Oil filter	First after 20 h, then at every second oil change (every 100 h), at least once a season⁶³
Fuel filter	Replace at least once a season, together with the extra water-separating filter if one is fitted⁶³
Strainer clean	Clean the feed pump strainer at least once a season⁶³
Air filter	Clean every 100 h or once a season: wash in diesel, then re-oil⁶³
Raw water impeller	No fixed interval: check the cooling system every 100 h or once a season, and inspect the impeller whenever the engine runs hot⁶³
V-belt check	Check the tension every 14 days: about 5 mm deflection⁶³
V-belt replace	Inspect every 100 h or once a season; replace if worn or cracked⁶³
Anode	Drive and propeller anodes: check every 100 h or once a season; replace when more than half is gone⁶³
Gearbox oil change	MS-B/MS2 reverse gear: every 200 h or at least once a season; check the level every 14 days⁶³
Saildrive oil	110S/120S: every 200 h or at least once a season; check the level every 14 days⁶³
Valve clearance	Listed with the 50-hour checks in the MD7A service scheme, and after every retightening of the cylinder head nuts, which are check-tightened every 100 h or once a season (workshop job)⁶³
Injectors	Every third season: opening pressure, leakage and spray pattern tested by a diesel workshop⁶³
Rubber seal (drive to hull)	120S: replace every 5 years (MD7B manual)⁶⁴

From Volvo Penta’s MD7A instruction book (1980); the 120S hull seal interval comes from the MD7B operator’s manual (1981). Hours or season, whichever comes first.

Specifications

Versions	MD7A with MS-B reverse gear, or MD7A/110S with saildrive; MD7B/MS2 with reverse gear, or MD7B/120S with saildrive^63,64
Cylinders	2, in-line, four-stroke⁶³
Displacement	0.744 l (45.4 cu in)⁶³
Bore × stroke	76.0 × 82.0 mm⁶³
Injection	Direct injection, CAV DPA distributor-type pump⁶³
Power	MD7A: 9.6 kW (13 hp) at 2600 rpm; MD7B: 12.5 kW (17 hp) at 3000 rpm (DIN continuous rating at the propeller shaft)⁶⁴
Rated speed	MD7A: 2600 rpm; MD7B: 3000 rpm⁶³
Idle speed	MD7A: 650–780 rpm; MD7B: 660–780 rpm⁶⁴
Cooling	Direct raw-water cooling with thermostat; on the saildrive versions the water comes in through the drive leg⁶³
Thermostat opens at	60 °C, fully open at 75 °C (MD7A) / 74 °C (MD7B)⁶³
Engine oil capacity	MD7A: 2.8 l with filter, 2.5 l without. The MD7B manual gives 3.0 l with filter and 2.8 l without in its data table, but 2.5 l on its oil-change page: fill to the dipstick mark^63,64
Engine oil grade	API CD; SAE 20W/30 (or single-grade SAE 20) above +10 °C, SAE 10W below +10 °C⁶³
Gearbox	MD7A: MS-B reverse gear 1.91:1 or 110S saildrive 1.66:1; MD7B: MS2 reverse gear 2.4:1 or 3.0:1 (parts catalogue: 2.37:1 / 3.02:1) or 120S saildrive 2.2:1^64,52
Gearbox oil	Engine oil, same as the engine: MS-B 0.6 l, MS2 0.8 l^64,63
Drive oil capacity	Engine oil, same as the engine: 110S 2.3 l, 120S 2.2 l^64,63
Compression pressure	20–24 kp/cm² (285–340 psi) at cranking speed⁶³
Valve clearance (hot)	0.30 mm inlet and exhaust, set on a warm engine (MD7A book)⁶³
Injection pressure	180–188 kp/cm² (2560–2675 psi)⁶³
Injection timing	10–12° BTDC (MD7A book)⁶³
Tightening torques	Cylinder head nuts 70 Nm (7 kpm); injector yoke nuts 8 Nm (MD7B manual)⁶⁴
Alternator	12 V; MD7A 35 A (420 W), MD7B 50 A⁶⁴
Starter motor	MD7A 0.8 kW, MD7B 1.1 kW⁶⁴
Battery	12 V, max. 70 Ah⁶⁴
Weight	MD7A: 175 kg with reverse gear, 192 kg with 110S; MD7B: 166 kg with MS2, 181 kg with 120S⁶⁴
Max. installation angle	15° rearwards; sideways underway 15° (MD7A) / 10° (MD7B)⁶⁴
Predecessor	Volvo Penta MD6A/MD6B: 2 cylinders, 0.631 l (70 × 82 mm), 10 hp at 2400 rpm, MS reverse gear; oil 3.0 l with filter, 2.8 l without; valve clearance 0.30 mm⁶⁵

Good to know

Oil changes come round quickly on these engines: every 50 hours, with a new filter at every second change. A season with a lot of motoring can mean two or three changes.⁶³
The MS-B and MS2 reverse gears and the 110S/120S saildrives take the same API CD engine oil as the engine, not ATF and not hypoid gear oil.⁶³
On the early pumps, pull impeller and shaft out only as far as you need to reach the hub screw: pushing the shaft back in from further out can damage its seals. If impeller and shaft turn freely against each other, the drive between them is worn.⁶³
Two fuel filter housings were fitted over the years, 829992 and later 840531, and they take different elements (829993 and 829913). Check which one you have before ordering, then bleed the system at the filter’s vent screw with the hand primer.¹¹
On saildrive boats the cooling water comes in through slots in the leg: clear them of growth whenever the boat is out of the water. When draining with the boat afloat, close the cock first and open it again before starting.⁶³
The MD7B manual gives the 120S rubber hull seal a 5-year replacement interval. On a drive this old, find out how old the seal is before you trust it.⁶⁴

Fitted in

Boats whose builder lists it as standard or optional equipment:

Westerly Centaur — Volvo Penta MD7A 13 hp (Alternative to the MD11C in the 1977 brochure and the price lists of 1977 to 1980, against a credit (£250 in 1977 and 1978, £281 in 1980); standard engine, with a two-blade propeller, of the fin-keeled Pembroke, and of the Centaur in the Dutch dealer’s list of January 1979)

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Sources

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