Volvo Penta · Inboard diesel

Volvo Penta MD2B

The MD2B is a two-cylinder Volvo Penta diesel with direct raw-water cooling and direct injection: 1.12 litres, two separate cylinder heads, a decompression lever with hand-start shaft, and either a Dynastart starter-generator or a starter motor plus alternator. Volvo Penta rated it at 25 hp (DIN) at 2500 rpm, later at 17 kW (23 hp) at the propeller shaft; it was built alongside the single-cylinder MD1B and the three-cylinder MD3B, which share many service parts. It came with the RB reverse gear, which runs on the engine oil, or the MS gear with its own sump. It grew out of the earlier MD2 (0.89 litres, about 16 hp); the part numbers on this page are confirmed for the MD2B only, not for the MD2 or MD2A.

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 MD1B, MD2B, MD3B (scanned) Operation manual pubs.volvopenta.com · PDF · EN
Supplement: hydraulic equipment MD2B HY Operation manual pubs.volvopenta.com · PDF · EN
Instruction book MD2 (predecessor, scanned) Operation manual pubs.volvopenta.com · PDF · EN
Product leaflet MD2B (25 hp, RB or MS gear) Product leaflet pubs.volvopenta.com · PDF · EN
Product leaflet MD2B (17 kW / 23 hp, MS gear) Product leaflet pubs.volvopenta.com · PDF · EN
Brochure MD1B, MD2B, MD3B Brochure pubs.volvopenta.com · PDF · EN
Product leaflet MD2 (15.5 hp) Product leaflet pubs.volvopenta.com · PDF · EN
Product bulletin MD1/MD2 Product leaflet pubs.volvopenta.com · PDF · EN
Volvo Penta manuals & handbooks: MD2B (workshop manual listed, print only) Manual portal volvopenta.com · EN
Volvo Penta manuals & handbooks: MD2 Manual portal volvopenta.com · EN
Volvo Penta manuals & handbooks: MD2A (no instruction book online) Manual portal volvopenta.com · EN
Volvo Penta parts catalogue, filtered to MD2B Parts catalogue volvopenta.com · EN
Parts catalogue: cooling system, intake and exhaust manifold MD2B Parts catalogue volvopenta.com · EN
Maintenance quick guide MD2B (Volvo Penta dealer Marine Parts Europe) Parts catalogue marinepartseurope.com · EN

Wear parts & part numbers

Part	OEM number	Also fits	Note
Impeller kit (with gasket)	`3586494`^1,2,3,4,5,6replaces 875807	—	The kit in Volvo Penta’s MD1B/MD2B on-board kits and the MD2B maintenance quick guide. A UK dealer gives the MD2B impeller as 39.5 mm across, 12 mm bore, 19 mm wide, 6 blades. With replacement pump 858065 use 21951342, with pump 829895 use 22222936.
Impeller kit (with gasket)	`21951342`^7,8,9replaces 3586496	—	Only for the replacement pump 858065 (fitted instead of 807368/833415, or 833522/833883 on the MD2B HY). Includes cover gasket 833994.
Impeller kit (with gasket)	`22222936`^10,11,8,12replaces 3593659	—	Only if your engine carries sea-water pump 829895 (earlier 825916), an alternative type the catalogue lists for MD1B/MD2B/MD3B/AQD2B.
Raw water pump	`858065`^7,8,13,14,15replaces 807368replaces 833415replaces 833522replaces 833883	—	Current Volvo Penta pump, replacing 807368 and 833415 (standard MD2B) and 833522/833883 (MD2B HY). Takes impeller kit 21951342.
Engine oil filter	`22057107`^16,17,5,18replaces 834337	—	Number in Volvo Penta’s MD2B maintenance quick guide and at a UK dealer (76 mm diameter, 62 mm seal, 59 mm high); the parts catalogue shows 834337.
Fuel filter (engine)	`829913`^19,20,21,22	—	For filter housing 840532, which replaces the original Bosch-type housing 803323.
Fuel filter (engine)	`21492771`^5,23	—	Current spin-on filter in the MD2B maintenance quick guide and at a UK dealer (76 mm diameter, 80 mm high); the quick guide also gives insert kit 23686345.
Fuel filter (engine)	`870065`^20,24	—	Insert only for engines that still have the original Bosch-type housing 803323.
Thermostat	`876080`^13,25,26,5	—	Late type, marked 62 °C; also in the maintenance quick guide. Housing seal 416033 and O-ring 955989 are separate parts.
Alternator V-belt	`966906`^2,27,5,28replaces 958306	—	900 mm, for later engines with starter motor and alternator. The earlier layout takes a 1025 mm belt (978515 in the quick guide).
Alternator V-belt	`966990`^1,29,30,5replaces 958367	—	Set of two 1300 mm belts for engines with the Dynastart starter-generator.
Cylinder head gasket	`859151`^31,32,33,34replaces 833070	—	One per cylinder head: the MD2B needs two.
Gasket set	`875502`^32,35,36	—	Decarbonising (top-end) set: head gaskets, valve cover gaskets 859120, exhaust manifold gaskets 859145, valve stem seals and more. Full overhaul set: 876389 (replaces 875503).
Exhaust mixing elbow	`833585`^13,32	—	Late-type exhaust riser; early engines have exhaust elbow 807193.
Exhaust elbow gasket	`859015`^32,37replaces 803374	—	Flange gasket for the exhaust riser.
Air filter	`833414`^13,38	—	Two cleanable intake filters per engine (catalogue: from engine no. 1303).
Gasket set	`875577`³⁹	—	Gasket set for the MS reverse gear (also MD1B, MD3B and AQD2B).
Ring anode	`833913`^40,41	—	Zinc anode on the propeller shaft, for 25 and 30 mm shafts; 833915 for 35 mm, 828140 for 40/45 mm.

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	After the first 20 h: oil and filter change, re-torque the cylinder heads (engine warm), then set the valve clearance⁴²
Engine oil change	Every 50 h or at least once a season (with the RB gear this changes the gear oil too); check the level daily⁴²
Oil filter	Every 100 h, together with the oil change⁴²
Gearbox oil change	MS gear: every 50 h or at least once a season; check the level daily⁴²
Fuel filter	Change the fine filter and clean the feed-pump pre-filter every 100 h or at least once a season⁴²
Air filter	Clean in diesel and re-oil every 100 h or once a season⁴²
V-belt check	Check tension every 50 h⁴²
Valve clearance	Every 100 h or at least once a season, and after re-torquing the heads⁴²
Season check	Re-torque the cylinder heads (engine warm) once each season⁴²
Injectors	Have them tested at a diesel workshop at least every 100 h⁴²
Cooling system	Check every 100 h or at least once a season; keep a spare impeller on board⁴²
Battery	Check the electrolyte every two weeks⁴²

From the MD1B/MD2B/MD3B instruction book (reprint 2001). Hours or season, whichever comes first.

Specifications

Versions	MD2B with Dynastart starter-generator or with starter motor and alternator; MD2B HY with hydraulic equipment; AQD2B is the Aquamatic version. Siblings: MD1B (1 cyl.), MD3B (3 cyl.)^42,43,39
Cylinders	2, in-line, four-stroke, direct injection⁴²
Displacement	1.12 l (88.9 × 90 mm)⁴²
Power	25 hp (DIN) at 2500 rpm; later literature: 17 kW (23 hp) at the propeller shaft^42,44
Maximum torque	7.2 kpm (52 lb ft) at 2000 rpm⁴⁵
Rated speed	2500 rpm⁴²
Idle speed	550–650 rpm⁴²
Compression pressure	20–24 kp/cm² (285–340 psi) at starter speed⁴²
Cooling	Direct raw-water cooling; sea-water pump on the timing gear housing, driven by the camshaft⁴²
Thermostat opens at	60 °C, fully open at 75 °C (instruction book); the current kit 876080 is marked 62 °C^42,13
Engine oil capacity	3.0 l without filter, 3.25 l with filter (engine incl. RB reverse gear)⁴²
Engine oil grade	API CD diesel engine oil (earlier: ‘DS’); SAE 20 above +20 °C, SAE 10W below +20 °C (as in the book)⁴²
Gearbox oil	MS gear: 0.60 l (0.50–0.60 l between the marks), same oil as the engine; the RB gear shares the engine sump⁴²
Valve clearance (hot)	Inlet 0.30 mm, exhaust 0.35 mm, set on a warm engine; decompression max. 0.5 mm⁴²
Injection pressure	170–178 kp/cm²; Bosch nozzle holder KBL 87S78/4, nozzle DLLA 150S720⁴²
Injection	Bosch injection pump PFR 2K 75A/381/11⁴²
Injection timing	23–26° before TDC⁴²
Alternator	12 V; alternator max. 450 W, or Dynastart starter-generator 135 W max. (90 W continuous)⁴²
Weight	Approx. 220 kg incl. reverse gear (instruction book, early leaflet); approx. 230 kg with MS 1.91:1 (later leaflet)^42,45,44
Gearbox	Volvo Penta RB 1.87:1 ahead, 1.7:1 astern (3.42:1 with additional reduction gear), or MS (Mono Shift) 1.91:1⁴²
Tightening torques	Cylinder head bolts 11.0 kpm (80 lb ft) on 19 mm hex, 4.5 kpm (33 lb ft) on 15 mm hex; con-rod bolts 6.5 kpm; intermediate main bearing 8.0 kpm; injector nuts 2.0 kpm⁴²
Predecessor	MD2: 2 cyl., 0.890 l (79.37 × 96 mm), 16.5 hp at 2300 rpm (leaflet: 15.5 hp), RB gear 1.87:1, approx. 190–200 kg; valve clearance and oil volumes as on the MD2B^46,47

Good to know

Identify your raw water pump before ordering an impeller: the catalogue shows the original MD2B pumps (807368/833415), the current replacement 858065 and an alternative type 829895, and they take three different impeller kits (see the notes in the parts table). Compare with your old impeller before you order.⁸
With the RB gear, engine and gearbox share one sump, so one oil change covers both. The MS gear has its own 0.6 l sump that has to be drained or pumped out separately.⁴²
On the MD2B the oil strainer has to come out before you can pump the sump empty through the dipstick tube; check its seal when you refit it.⁴²
When laying up, drain the cooling water from the block through the drain cocks on the starboard side (three on the MD2B): the rust-proofing flush alone does not protect against frost.⁴²
Dynastart belts should give about 3–4 mm under thumb pressure. An alternator belt is tight enough when you can only just make the pulley slip by turning a fan blade with one finger.⁴²
When refitting the sea-water pump cover, use a gasket of the original thickness (the book stresses this) and turn the impeller by hand to check that the pump coupling is undamaged.⁴²

Fitted in

Boats whose builder lists it as standard or optional equipment:

Tayana 37 — Volvo Penta MD3B · MD2 (Early hulls of the late 1970s: according to TOG News many of them had Volvo Penta engines, naming the MD-2 and MD-3; an owners’ table of 1980 lists an MD-3B)
Westerly Centaur — Volvo Penta MD2 (1968 brochure and price lists: two-cylinder diesel as an extra, 15 hp in the brochure and the September list, 16.5 hp in the December list, with a 12 V battery, remote controls, a stern-gland greasing system and a 10-gallon fuel tank)
Westerly Centaur — Volvo Penta MD2B 25 hp (Recommended engine in the 1971 brochure; standard in the December 1974 price list and the brochure of December 1975: flexibly mounted, with alternator, reverse gear, electric start, instrument panel, water-cooled exhaust with silencer, remote controls and stern-gland greasing system)

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Sources

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