Yanmar · Inboard diesel

Yanmar 4JH3E

The 4JH3E is the naturally aspirated four-cylinder of Yanmar’s third JH generation: a direct-injection diesel of 1.995 l making 41 kW (56 hp) at 3800 rpm, a common original engine and repower in sailing yachts of roughly 36 to 45 ft from the late 1990s until the 4JH4 arrived in 2007. It replaced the 4JH2E and was sold next to the turbocharged 4JH3-TE and 4JH3-TCE and the intercooled 4JH3-HTE and 4JH3-DTE; Yanmar’s 2002 brochure lists it with KM3P, KM3A, KBW20-1 or KM4A1 gearboxes (4JH3E, 4JH3BE, 4JH3WE, 4JH3B4E), and the parts catalogue also has a saildrive version. This page covers the 4JH3E, 4JH3CE and 4JH3CE1; impeller, pump O-ring, raw-water pump, thermostat, belt, oil filter and coolant pump are catalogued for the turbo engines too, while fuel filter, exhaust elbow, head gasket and injectors differ. Yanmar publishes only the operation manual of the turbo versions, so the service schedule below is taken from it, without the turbo items.

Manuals & documents

Yanmar does not put the 4JH3E’s own operation manual online; its FAQ sends owners of engines no longer sold to a dealer. The first links go to Yanmar: the manual for the turbo 4JH3 versions, the page of the 4JH3-DTE, which is still sold, and the dealer and support pages. The parts catalogues are Yanmar’s own, hosted by Mécanique Plaisance and Léon Marine, and the 2002 brochure is hosted by Simplicity Marine Drives. We host no manuals or drawings.

Wear parts & part numbers

PartOEM numberAlso fitsNote
Impeller kit (with gasket)129670-426102,3,4,5,1replaces 129670-42530Parts4Engines P4E495201312161All 4JH3 (dealers list -E, -TE, -HTE and -DTE). The kit holds the later impeller 129670-42531, the cover O-ring and the cover screws and replaces the loose impeller 129670-42530 of the gear-driven pump.
Pump cover O-ringX0506590-012,3,6,5replaces X0506590—Seals the pump cover plate; 4JH3-E, -TE, -HTE and -DTE. Included in impeller kit 129670-42610.
Raw water pump cover plateX0146535-012,3,8replaces 129670-42520Parts4Engines P4E495201294127The same plate as on the 4JH4; the aftermarket plate comes with its O-ring.
Water pump plate129670-425403,9,10—Wear plate of the seawater pump; all 4JH3 (the catalogue lists it for all five versions), and Diesel Parts Direct lists it for later JH engines such as the 4JH45 and 3JH40 too. Yanmar’s manual for the turbo 4JH3 names a damaged wear plate as a reason to overhaul the pump.
Raw water pump129670-425142,3,11,12replaces 129670-42510replaces 129670-42501replaces 129670-42500Parts4Engines P4E4952013466511Gear-driven; all 4JH3 and the 4JH4E/-TE/-HTE. The catalogue runs 129670-42500 → -42501 → -42510 (from engine no. E22643 on the 4JH3E/CE), -42514 is the current number. Mounting gasket 129150-01881, from March 2012 129C26-01890.
Water pump gaskets129150-018813,13—Mounting gasket of the seawater pump, all 4JH3. From March 2012 the catalogue lists gasket 129C26-01890 as fully interchangeable.
Engine oil filter129150-351702,3,15,16,17,14replaces 129150-35153replaces 129150-35151Parts4Engines (Bosch) P4E4952013129614Spin-on, 80 mm; all 4JH3 (the catalogue prints 129150-35151, dealers supply 129150-35170), also 4JH2, 4JH4 and 4JH5.
Fuel filter (engine)129470-558102,3,19,20,21,18replaces 129470-55703replaces 129470-55701Parts4Engines (MANN) P4E4952013467318Element for the 4JH3E, 4JH3CE and 4JH3CE1 (filter assembly 129470-55601), the same as on the 4JH2 and the early 4JH4E. The turbo 4JH3-TE and -TCE use 129574-55710 (later -55711) instead.
Alternator V-belt25132-0046002,3,23,24,22Parts4Engines (Gates) P4E4952013322622A46, drives alternator and coolant pump; all 4JH3 (dealers also list the 4JH2 and early 4JH4-TE).
Thermostat129470-498012,3,25,26—76.5 °C; all 4JH3, and per dealers also 4JH2, 4JH4 and 4JH5.
Thermostat gasket129150-498112,3,27,28,29replaces 129470-49810—All 4JH3. The thermostat cover also takes gasket 129795-49551.
Coolant pump129470-420022,3,30replaces 129470-42001Parts4Engines P4E4952012871330All 4JH3; -42002 from engine no. E25450 (4JH3E/CE/CE1) and E12627 (4JH3-TE/TCE). Mounting gasket 129150-42020, from October 2002 129486-42050.
Heat exchanger end-cap O-ring24321-0007503,31—End-cap O-ring of the fresh-water cooler, two per engine, for the cooler fitted from engine no. E25003 (129473-44900; on the 4JH3-TE/-TCE from E12191). Earlier coolers take 24321-000800; the catalogue marks the two as not interchangeable, so check the engine number first.
Heat exchanger end-cap O-ring24321-0008003,32—The O-ring for coolers built before engine no. E25003 (cooler 129670-44900), two per engine; not interchangeable with the 24321-000750 of the later cooler.
Heat exchanger gasket120322-330503,33—End-cover gasket of the fresh-water cooler from engine no. E25003 (4JH3-TE/-TCE from E12191), one per engine, fitted together with O-ring 24321-000750.
Pressure cap129107-445903,34,35—Pressure cap on the fresh-water cooler, listed as a separate part from engine no. E24255 (filler neck 129171-44600). Earlier engines have filler assembly 129670-44600, which the catalogue lists as fully interchangeable with the later neck.
Exhaust mixing elbow129670-135612,3,36,37replaces 129670-13560—4JH3E, 4JH3CE and 4JH3CE1 only — the 4JH3-TE has its own elbow 129472-13500. The 4JH4AE catalogue lists -13561 as the interchangeable replacement from November 2007; the same elbow fits the 4JH4E/4JH4AE/4JH5E. Flange gasket 129472-18090.
Exhaust mixing elbow129470-135413,38—Optional elbow, shown in the catalogue drawing in place of the standard elbow 129670-13560; it comes with plug 129472-13560 and water pipe 129470-49050 and uses the same gasket 129472-18090. 4JH3E, 4JH3CE and 4JH3CE1.
Exhaust elbow gasket129472-180903,39—Gasket between mixing elbow and cooler; fits the standard elbow 129670-13560/-13561 and the optional elbow 129470-13541.
Exhaust manifold gasket129550-131103,40—Gasket between the fresh-water cooler, which also forms the exhaust manifold, and the cylinder head; all 4JH3.
Cylinder head gasket129408-013303,41—4JH3E, 4JH3CE and 4JH3CE1; the turbo 4JH3-TE/-TCE take 129693-01330.
Valve cover gasket129550-113103,42—Rocker cover gasket; the same on all 4JH3.
Fuel injector729670-531002,3,43—Complete injector, 4 per engine; 4JH3E, 4JH3CE and 4JH3CE1. Nozzle 129468-53000, seat gasket 129470-11920. The turbo 4JH3-TE/-TCE use 729671-53100 (later -53101).
Injector gasket129470-119203,44—Seat gasket under each injector, 4 per engine; the same on all 4JH3.
Stop solenoid129470-673203,45—12 V engine stop solenoid of the 4JH3E, 4JH3CE and 4JH3CE1.
Alternator129772-772003,46Parts4Engines P4E495201287104612 V 55 A, standard on the 4JH3E until engine no. E25682. The catalogue lists the later 60 A alternator 128271-77200 as a replacement for it (interchangeable in that direction only).
Alternator128271-772003,47—12 V 60 A, fitted from engine no. E25682 (4JH3E, 4JH3CE, 4JH3CE1); also replaces the earlier 55 A unit.
Starter motor129608-770103,48,49replaces 129698-77010—12 V 1.2 kW starter S114-817A, listed from January 2007 for the 4JH3E, 4JH3CE and 4JH3CE1. It replaces the original 129698-77010 only together with bracket 129573-77952 (catalogue Fig. 54).

Numbers checked against the sources below on 23 October 2026. Always confirm against your serial number and exact type before ordering.

Service intervals

TaskInterval
Oil level checkDaily before starting, together with the fuel level and a look for oil, water and fuel leaks10
First serviceAfter the first 50 h: change the engine oil and oil filter and the gearbox oil (washing the gearbox oil filter where there is one)10
Engine oil changeEvery 250 h or yearly, first time after 50 h10
Oil filterEvery 250 h or yearly, first time after 50 h10
Fuel filterDrain water from the filter every 50 h; replace the element every 250 h or yearly10
Drain fuel tankDrain water and sediment every 50 h10
BatteryCheck the electrolyte level every 50 h10
Coolant changeEvery 250 h or yearly10
V-belt checkCheck and adjust every 250 h or yearly: about 8–10 mm deflection under thumb pressure at mid-span10
Control cablesCheck and adjust the throttle and gear cables every 250 h or yearly10
Gearbox oil changeFirst after 50 h, again after 250 h, then every 1000 h or 4 years (KBW21, KM4A and KMH4A gearboxes in that manual)10
Valve clearanceAdjust every 500 h or 2 years; lap the valves every 1000 h or 4 years (dealer)10
InjectorsCheck injection pressure and spray pattern every 500 h or 2 years, injection timing every 1000 h or 4 years (dealer)10
Raw water impellerOpen and inspect the seawater pump every 1000 h or 4 years; replace the impeller every 2000 h10
Cooling systemClean the seawater and fresh-water circuits (pumps, oil coolers, fresh-water cooler, thermostat) every 1000 h or 4 years (dealer)10
Hoses & clampsCheck the fuel and cooling-water hoses every 1000 h or 4 years and replace damaged ones (dealer)10
Exhaust elbow checkReplace the mixing elbow every 1000 h or 4 years (dealer)10

Yanmar does not put the 4JH3E’s own operation manual online. This schedule comes from the one it does publish, for the turbocharged 4JH3-TE, -TCE, -HTE and -DTE (49961-202851, 1998); the turbocharger items are left out. Hours or time, whichever comes first. Have a Yanmar dealer confirm it for your engine and gearbox.

Specifications

Cylinders4, in-line, direct injection (one injector per cylinder)2,3,50
Models4JH3E, 4JH3CE, 4JH3CE1 (naturally aspirated) share one parts catalogue with the 4JH3-TE and 4JH3-TCE (turbo); 4JH3-HTE and 4JH3-DTE (turbo with intercooler) have their own2,3
Versions4JH3E with KM3P gearbox, 4JH3BE with KM3A angle drive, 4JH3WE with KBW20-1, 4JH3B4E with KM4A1 angle drive (Yanmar brochure, 2002)50
AspirationNaturally aspirated (the 4JH3-TE/-TCE are turbocharged, the 4JH3-HTE/-DTE turbocharged with intercooler)50
Displacement1.995 l (121.74 cu in)50
Bore × stroke84 × 90 mm50
Power41 kW (56 hp) at 3800 rpm maximum; 37 kW (50 hp) at 3650 rpm continuous (at the crankshaft, ISO 3046/1)50
Rated speed3800 rpm (continuous rating at 3650 rpm)50
InjectionYanmar plunger-type injection pump with one plunger per cylinder, governor and fuel feed pump built in; the turbo 4JH3-TE/-TCE use a Bosch-type VE distributor pump (Zexel) instead3,10
CoolingFresh-water cooled with heat exchanger; belt-driven coolant pump, gear-driven rubber-impeller sea-water pump2,3,50
Thermostat opens at76.5 °C2,3
Starter motor12 V, 1.2 kW (129698-77010; from January 2007 the S114-817A, 129608-77010); 12 V intake air heater for cold starts50,3
Alternator12 V 55 A (129772-77200) as standard; from engine no. E25682 the catalogue lists a 12 V 60 A unit (128271-77200), and a 12 V 80 A alternator (119573-77201) as an option3,50
GearboxMechanical, with these ratios: KM3P (parallel; 2.36 / 2.61), KM3A (angle drive 7°; 2.33 / 2.64), KBW20-1 (2.17 / 2.62 / 3.28) or KM4A1 (angle drive 7°; 1.47 / 2.14 / 2.63 / 3.30); the parts catalogue also lists mounting parts for a KBW21 gearbox and a saildrive version50,3
Direction of rotationCrankshaft counterclockwise, propeller shaft clockwise, both seen from astern; with the KM4A1 the propeller can turn either way50
Dry weight223 kg with KM3P or KM3A, 236 kg with KBW20-1, 238 kg with KM4A150
EmissionsMeets the European BSO (Lake Constance) limits, according to Yanmar’s 2002 brochure50

Good to know

  • Yanmar publishes only the operation manual of the turbo versions (4JH3-TE/-TCE/-HTE/-DTE, 49961-202851), on its 4JH3-DTE product page; for the 4JH3E’s own manual its FAQ sends owners of engines no longer sold to a dealer. The turbo manual’s service schedule is a good guide, but its specifications, fuel filter and injection pump are not the 4JH3E’s.51,52,10,3
  • Have the engine serial number ready when ordering: the catalogue shows running changes on the 4JH3E at engine numbers E20576 (intake manifold), E21010 and E21367 (fuel pipes), E22126 and E22643 (raw-water pump), E24255 (coolant filler and pressure cap), E25003 (fresh-water cooler and its O-rings), E25450 (coolant pump) and E25682 (alternator), plus dated changes in 2002, 2003, 2007, 2008 and 2012.2,3
  • Fit a new cover O-ring every time you change the impeller. The current Yanmar kit 129670-42610 already contains impeller, O-ring and cover screws; Yanmar’s impeller removal tool is 129671-92110. The manual for the turbo 4JH3 has the pump opened and inspected every 1000 h and the impeller replaced every 2000 h.5,10
  • Check the model on the engine plate before buying filters: the naturally aspirated 4JH3E/CE/CE1 and the turbo 4JH3-TE/-TCE use different fuel filter elements, exhaust elbows and injectors, while oil filter, thermostat, belt and impeller are the same.2,3
  • There is no zinc anode on the engine itself: neither the 4JH3E parts catalogue nor Yanmar’s manual for the turbo 4JH3 lists one, in the heat exchanger or anywhere else. Corrosion protection sits on the propeller shaft or the saildrive, so check those anodes instead.3,10
  • Many 4JH3 service parts are shared across four JH generations — thermostat 129470-49801 from the 4JH2 to the 4JH5, oil filter 129150-35170, impeller kit 129670-42610 — so parts listed for a 4JH2E, 4JH4E or 4JH5E usually fit, which widens the pool of new and used parts.25

Videos & how-tos

Links to YouTube, nothing embedded. The maker’s own channel comes first; the rest are channels we found clear and correct for this model.

Fitted in

Boats whose builder lists it as standard or optional equipment:

  • Najad 400 — Yanmar 4JH3-E (September 2003 specification: four cylinders, direct injection, fresh-water cooling, 41.2 kW (56 hp))
  • Pacific Seacraft 37 — Yanmar 4JH3E (Spec sheet of September 2002: four cylinders, 56 hp, fresh-water cooled, 3″ exhaust, 80 A alternator, Yanmar ‘C’ panel under a clear cover in the cockpit, hour meter below deck)

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Sources

  1. parts4engines.com/products/yanmar-jh-series-raw-water-pump-impeller-kit
  2. mecanique-plaisance-finistere.com/yanmar/pdfmoteur/4jh3e.pdf
  3. leon-marine.com/wp-content/uploads/2021/02/4JH3-E.pdf
  4. dieselpartsdirect.com/ym12967042610
  5. shop.marinedieselinc.com/products/129670-42610
  6. dieselpartsdirect.com/ymx050659001
  7. parts4engines.com/products/yanmar-4jh-raw-water-pump-cover-plate
  8. dieselpartsdirect.com/ymx014653501
  9. dieselpartsdirect.com/ym12967042540
  10. yanmar.com/media/global/com/product/marinepleasure/sailBoatPropulsion/operationmanual/4JH…
  11. parts4engines.com/products/yanmar-4jh-raw-water-pump
  12. dieselpartsdirect.com/ym12967042514
  13. dieselpartsdirect.com/ym12915001881
  14. parts4engines.com/products/yanmar-4jh-oil-filter
  15. dieselpartsdirect.com/ym12915035170
  16. dieselpartsdirect.com/ym12915035153
  17. shop.marinedieselinc.com/products/129150-35170
  18. parts4engines.com/products/yanmar-4jh-fuel-filter
  19. dieselpartsdirect.com/ym12947055810
  20. dieselpartsdirect.com/ym12947055703
  21. shop.marinedieselinc.com/products/129470-55810
  22. parts4engines.com/products/yanmar-3jh-and-4jh-alternator-belts
  23. dieselpartsdirect.com/ym25132004600
  24. shop.marinedieselinc.com/products/25132-004600
  25. dieselpartsdirect.com/ym12947049801
  26. shop.marinedieselinc.com/products/129470-49801
  27. dieselpartsdirect.com/ym12947049810
  28. dieselpartsdirect.com/ym12915049811
  29. shop.marinedieselinc.com/products/129150-49811
  30. parts4engines.com/products/yanmar-4jh-series-water-pump
  31. dieselpartsdirect.com/ym24321000750
  32. dieselpartsdirect.com/ym24321000800
  33. dieselpartsdirect.com/ym12032233050
  34. dieselpartsdirect.com/ym12910744590
  35. dieselpartsdirect.com/ym12917144600
  36. mecanique-plaisance-finistere.com/yanmar/pdfmoteur/4jh4ae.pdf
  37. dieselpartsdirect.com/ym12967013561
  38. dieselpartsdirect.com/ym12947013541
  39. dieselpartsdirect.com/ym12947218090
  40. dieselpartsdirect.com/ym12955013110
  41. dieselpartsdirect.com/ym12940801330
  42. dieselpartsdirect.com/ym12955011310
  43. dieselpartsdirect.com/ym72967053100
  44. dieselpartsdirect.com/ym12947011920
  45. dieselpartsdirect.com/ym12947067320
  46. parts4engines.com/products/yanmar-4jh-alternator-12v-55-amp
  47. dieselpartsdirect.com/ym12827177200
  48. dieselpartsdirect.com/ym12960877010
  49. dieselpartsdirect.com/ym12969877010
  50. simplicity-marine.com/pdf/Yanmar/JH.pdf
  51. yanmar.com/marine/service/faq/
  52. yanmar.com/marine/product/engines/4jh3-dte/

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