Yanmar · Inboard diesel

Yanmar 4JH2E

The 4JH2E is the naturally aspirated four-cylinder of Yanmar’s 4JH2 family, rated at about 50 hp at 3,600 rpm — a widespread auxiliary in larger sailing yachts of the late 1980s and 1990s. The same base engine was sold turbocharged (4JH2-TE) and with intercooler (4JH2-HTE, -DTE, -UTE); one Yanmar parts catalogue covers all five: impeller, thermostat, belt and oil filter are shared, while injectors and mixing elbow differ between the 4JH2E and the turbo versions. Yanmar’s own site no longer offers the operation manual; an archived copy of Yanmar Europe’s PDF is linked above, and a Yanmar dealer can supply the current print. Several wear parts carry over to the later 4JH3 to 4JH5.

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

Manuals & documents

The links go to Yanmar’s own documents — some as archived copies of pages the maker has since taken down. We host no manuals or drawings.

Yanmar FAQ: how to get the manual of an engine no longer sold Manual portal yanmar.com · EN
Yanmar dealer & distributor network Manual portal yanmar.com · EN
Yanmar service & genuine parts, maintenance kits Manual portal yanmar.com · EN
Yanmar Marine Support Portal (engine registration, technical enquiries) Manual portal yanmar.com · EN
Parts catalogue 4JH2E / -TE / -HTE / -DTE / -UTE, 0CR10-M35102EN (September 2014 update), hosted by Léon Marine in Sète, a Yanmar specialist whose authorised-dealer status we could not confirm Parts catalogue leon-marine.com · PDF · EN
Parts catalogue 4JH2E / -TE / -HTE / -DTE / -UTE (hosted by Yanmar dealer Mécanique Plaisance) Parts catalogue mecanique-plaisance-finistere.com · PDF · EN
Operation manual JH(2) series, 49961-201372 (covers 4JH2E, 4JH2-TE, -HTE, -DTE, -UTE plus 3JH2 and 4JHE; Yanmar Europe download, archived) Archived maker page web.archive.org · PDF · EN

Wear parts & part numbers

Part	OEM number	Also fits	Note
Raw water pump impeller	`129470-42532`^1,2,3,4replaces 129470-42530	—	4JH2E and the turbo variants (gear-driven pump). Seal the cover with a new O-ring.
Pump cover O-ring	`24341-000600`^1,5,3,4	—	All 4JH2 variants.
Water pump gaskets	`129150-01881`^1,3,6,4	—	Pump-to-gear-case mounting gasket, all 4JH2 from January 1991; earlier engines used another gasket.
Raw water pump cover plate	`129470-42520`^4,7	—	Cover plate of the seawater pump, all 4JH2 variants; Yanmar’s 4JH2 spare-parts kit has it next to the impeller.
Raw water pump	`129573-42500`^4,1	—	Complete gear-driven seawater pump, all 4JH2 variants, as listed in the 2014 parts catalogue; quote your serial number, the dealer will know a later number if there is one.
Coolant pump	`129470-42003`^8,4replaces 129470-42001replaces 129470-42000	—	Coolant pump, all 4JH2 variants. The catalogue lists -42000 and, from January 1991, -42001; the US dealer Marine Diesel sells the genuine -42003 for the 4JH2E. Mounting gasket 129150-42020.
Engine oil filter	`129150-35170`^1,9,10,4replaces 129150-35150replaces 129150-35153	—	Spin-on, 90 × 80 mm; 4JH2E and all turbo variants.
Fuel filter (engine)	`129470-55810`^{1,11,12,4,13,14}replaces 129470-55701replaces 129470-55700replaces 129470-55703	—	Element for 4JH2E, -TE, -HTE and -DTE. The 4JH2-UTE uses 129574-55711 (formerly 129574-55710).
Fuel lift pump	`129158-52101`^15,4replaces 129158-52100	—	Mechanical feed pump with hand primer, 4JH2E, -TE, -HTE and -DTE (the -UTE has a different fuel system). The 2014 catalogue lists -52100; Marine Diesel sells -52101 for these engines.
Air filter	`129470-12330`^4,16,17	—	Washable element in the intake silencer: 4JH2E built before July 1990 and all turbo variants. The later 4JH2E silencer 129570-12300 has no separately listed element.
Thermostat	`129470-49801`^1,18,19,4	—	76.5 °C; all 4JH2 variants, and per dealers also 4JH3, 4JH4 and 4JH5.
Thermostat gasket	`129150-49811`^1,20,21,4replaces 129470-49810	—
Alternator V-belt	`25132-004600`^1,22,4,23	—	A46, alternator and coolant pump; all 4JH2 variants (dealers also list 4JH3 and early 4JH4-TE).
Pressure cap	`123682-44210`^4,24	—	Pressure cap on the heat exchanger filler, all 4JH2 variants.
Heat exchanger end-cap O-ring	`24321-000750`^4,25	—	1AG75.0, two per engine for the heat exchanger end covers: 4JH2E and 4JH2-TE.
Heat exchanger end-cap O-ring	`24321-000800`^4,26	—	1AG80.0, two per engine: 4JH2-HTE, -DTE and -UTE.
Heat exchanger gasket	`120322-33050`^4,27	—	End-cover gasket, listed for the 4JH2E and 4JH2-TE.
Exhaust manifold gasket	`129550-13110`^4,28	—	Between cylinder head and the heat exchanger housing, which doubles as exhaust manifold; all 4JH2 variants.
Exhaust mixing elbow	`129470-13560`^4,1	—	4JH2E only: elbow on the heat exchanger outlet. Number from the 2014 parts catalogue.
Exhaust elbow gasket	`129472-18090`^4,29	—	4JH2E elbow gasket; the turbo versions use the same gasket under the turbocharger.
Exhaust mixing elbow	`129792-13552`^4,30	—	Turbo variants (-TE, -HTE, -DTE, -UTE): elbow on the turbocharger outlet.
Exhaust elbow gasket	`129472-13520`^4,31	—	Turbo variants: gasket between turbocharger and elbow.
Fuel injector	`729570-53200`^4,32replaces 729570-53100	—	4JH2E, four per engine.
Fuel injector	`729595-53100`^4,33	—	4JH2-TE and -HTE, and early 4JH2-UTE.
Fuel injector	`729573-53050`^4,34replaces 729573-53100	—	4JH2-DTE and later 4JH2-UTE.
Injector gasket	`129685-11930`^4,35,36replaces 129470-11920	—	Four per engine, all 4JH2 variants.
Valve cover gasket	`129550-11310`^4,37,38	—	All 4JH2 variants.
Cylinder head gasket	`129573-01351`^4,39	—	Standard thickness, all 4JH2 variants; Yanmar also lists 1.3 and 1.5 mm gaskets for adjustment.
Gasket set	`729573-92601`⁴	—	Engine gasket set, all 4JH2 variants (number from the 2014 parts catalogue).
Engine mount	`121370-08351`^4,40	—	Flexible mount type 150; the catalogue lists two of these and two type 200 per engine.
Engine mount	`129470-08350`^4,41	—	Flexible mount type 200, two per engine.
Pressure switch	`124060-39452`^42,43,4	—	Oil pressure switch (0.2 kg/cm²) for the warning lamp, not a gauge sender; the 2014 catalogue still lists 124060-39451.
Starter motor	`171008-77010`^4,44,17	—	S114-483, 12 V 1.4 kW, all 4JH2 variants.
Alternator	`129772-77200`^4,45	—	12 V 55 A, all 4JH2 variants.

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

Service intervals

Task	Interval
First service	After the first 50 h or first month: change engine oil, oil filter and gear oil, drain the fuel tank, retension the V-belt, check the remote control; the dealer adjusts the valve clearance and checks shaft alignment¹⁷
Engine oil change	Every 150 h, first time after 50 h¹⁷
Oil filter	Every 300 h, first time after 50 h¹⁷
Gearbox oil change	Every 150 h, first time after 50 h¹⁷
Fuel filter	Every 300 h¹⁷
Drain fuel tank	Every 300 h, first time after 50 h¹⁷
V-belt check	Every 300 h, first time after 50 h¹⁷
Raw water impeller	Replace every 600 h¹⁷
Coolant change	Yearly¹⁷
Air filter	Wash the intake silencer element in mild detergent every 300 h¹⁷
Exhaust elbow check	Clean the mixing elbow every 300 h¹⁷
Crankcase ventilation	Clean the breather pipe every 300 h¹⁷
Turbocharger wash	Turbo variants: wash the compressor every 150 h, every 50 h if washed with fresh water only (dealer)¹⁷
Electrical connections	Check the wiring connectors every 300 h¹⁷
Injectors	Check injection timing and spray pattern every 600 h (dealer)¹⁷
Valve clearance	First at 50 h, then every 600 h (dealer)¹⁷
Retighten cylinder head bolts	Retighten the cylinder head bolts and the main nuts and bolts every 600 h (dealer)¹⁷
Control cables	Check the remote control after the first 50 h, then every 600 h¹⁷
Engine alignment	Check shaft alignment after the first 50 h, then every 600 h (dealer or yard)¹⁷
Storage / winterising	Laid up for 3 months or more: change oil and oil filter, run the engine once a month if possible, keep the coolant in if it is not too old, charge the batteries every month¹⁷

From Yanmar’s JH(2) series operation manual (49961-201372) for the 4JH2E and all turbo versions. Apart from the first service (after 50 h or one month) and the yearly coolant change it counts engine hours only, without calendar limits. The KBW or KM gearbox has its own manual.

Specifications

Cylinders	4 in-line, four-stroke, water-cooled, direct injection^17,1
Models	4JH2E (naturally aspirated), 4JH2-TE (turbo), 4JH2-HTE / -DTE / -UTE (turbo with intercooler)^17,1
Displacement	1.817 l¹⁷
Bore × stroke	82 × 86 mm¹⁷
Power	4JH2E: 37.5 kW (51 hp) at 3600 rpm one-hour rating, 33.8 kW (46 hp) at 3400 rpm continuous; one-hour rating of the others at 3600 rpm: -TE 46.5 kW (63 hp), -HTE 56.0 kW (76 hp), -DTE 65.0 kW (88 hp), -UTE 74.0 kW (101 hp)¹⁷
Compression ratio	4JH2E 18.1:1; -TE and -HTE 18.0:1; -DTE and -UTE 17.2:1¹⁷
Firing order	1-3-4-2¹⁷
Injection	Yanmar in-line pump YPES-CL (4JH2E to -DTE), distributor pump VE on the -UTE; hole-type nozzles¹⁷
Injection timing	4JH2E 10° ± 1° BTDC; -TE 12°, -HTE 14°, -DTE 10°, -UTE 12° (each ± 1°)¹⁷
Injection pressure	220 ± 5 kgf/cm² (about 21.6 MPa), all variants¹⁷
Direction of rotation	Crankshaft anticlockwise seen from the stern; propeller shaft clockwise seen from the stern (KBW21), KM4A for either direction¹⁷
Cooling	Fresh-water (coolant) circuit with heat exchanger and centrifugal pump; seawater pump with rubber impeller¹⁷
Thermostat opens at	76.5 °C^1,4
Engine oil capacity	7.0 l maximum at a 0° installation angle; 2.5 l between the dipstick marks¹⁷
Engine oil grade	API CD; viscosity by ambient temperature, e.g. SAE 10W-30 (−20 to +30 °C) or 20W-40 (−10 to +40 °C)¹⁷
Coolant capacity	6.0 l in the engine + 0.8 l in the reservoir¹⁷
Coolant	Clean tap water with anti-rust additive, antifreeze where it can freeze; never seawater or hard well water¹⁷
Fuel	Diesel, cetane number above 45, sulphur below 0.5 %, water below 0.1 %¹⁷
Starter motor	12 V, 1.4 kW¹⁷
Alternator	12 V 55 A (80 A optional)¹⁷
Battery	12 V, 120 Ah recommended¹⁷
Belt tension	About 10 mm deflection under 10 kg thumb pressure¹⁷
Dry weight	With gearbox: 4JH2E 226 kg and -TE 232 kg (KBW20, 898 × 561 × 635 mm); -HTE, -DTE and -UTE 246 kg (KBW21, 898 × 561 × 644 mm)¹⁷
Gearbox	KBW20 (4JH2E, -TE) or KBW21 (-HTE, -DTE, -UTE); also KM4A (1.47, 2.14, 2.63 or 3.30:1) or KM3P2 (2.36 or 2.61:1 ahead)^17,1
Gearbox oil	KBW gearboxes: ATF type A; KM gearboxes: the engine oil, never ATF (KM4A 1.3 l, KM3P2 0.35 l)¹⁷

Good to know

Yanmar does not publish the 4JH2 operation manual online; its FAQ says manuals for engines no longer sold come from dealers. Ask a Yanmar dealer for the manual and the service schedule.⁴⁶
Have the serial number ready when ordering: Yanmar made several running changes to the 4JH2, for example the intake silencer in July 1990 and the fuel filter element and pump gasket in January 1991.^1,4
Replace the pump cover O-ring (24341-000600) every time you change the impeller — it is a separate part number, not part of the impeller.^5,3
The 4JH2-UTE takes a different fuel filter from the 4JH2E, -TE, -HTE and -DTE — check the model on the engine plate before buying filters.^1,4,14
Some service parts carry over to later JH engines — the 76.5 °C thermostat 129470-49801 also fits the 4JH3, 4JH4 and 4JH5 — which widens the pool of new and used parts.^18,19
Long spells at low idle (below 1000 rpm for more than two hours, for example charging batteries at anchor) leave carbon on injectors, valves and turbocharger; the manual asks for one minute above 2500 rpm after every two hours of idling.¹⁷

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.

Changing the raw water impeller on a 4JH2E Video Sailing Sea-Renity · EN · 7 min
Impeller replacement on the turbocharged 4JH2-TE Video Chris Glubka · EN · 11 min
Oil change on the 4JH2E of a Catalina 42 Video Sailing Sea-Renity · EN · 10 min
4JH2-DTE service: impeller, oil and oil filter, fuel filter, seawater strainer (Italian) Video Lorenzo Cardoselli · IT · 13 min

Fitted in

Boats whose builder lists it as standard or optional equipment:

Island Packet 38 — Yanmar 4JH2E (50 hp) (Later boats: the yard’s model tables give 44 or 50 hp; Yanmar’s naturally aspirated 50 hp four-cylinder of those years is the 4JH2E, and a 1992 boat in the IPYOA classifieds has one)
Pacific Seacraft 37 — Yanmar 4JH2E (Yard lists of 1997 (Classic and Voyagemaker) and June 2000 and the brochure: four cylinders, 51 hp, fresh-water cooled, 80 A alternator, mechanical fuel pump with an electric back-up pump, seawater strainer on a bulkhead and a waterlift muffler)
Tayana 37 — Yanmar 4JH2E (Undated Ta Yang brochure for cutter, ketch and pilothouse: ‘Diesel engine by Yanmar 4JH2E 50HP’ in the standard equipment list)

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Sources

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