Yanmar 4JH3-DTE 125HP Diesel Marine Inboard Engine
The Yanmar 4JH3-DTE 125HP Marine Diesel Engine is a compact, four-cylinder marine propulsion engine with a displacement of 1.995 litres and a rated output of 91.9 kW / 125 MHP at 3,800 rpm. Designed for pleasure-boat propulsion, it combines direct diesel injection with turbocharging and intercooling in a relatively lightweight inboard package.
With freshwater cooling, mechanical engine controls and compatibility with marine gearbox options, the 4JH3-DTE is particularly relevant to boat owners, marine professionals and repower specialists requiring a compact Yanmar diesel propulsion solution.
Overview
The Yanmar 4JH3-DTE belongs to Yanmar’s established JH-series marine diesel engine family.
It uses an inline four-cylinder, four-stroke, water-cooled configuration with 1.995 litres of displacement. Its relatively compact capacity is combined with turbocharging and intercooling to produce a maximum rated output of 125 MHP (91.9 kW) at 3,800 rpm.
The engine uses direct fuel injection with a Bosch distributor-type VE injection pump and mechanical controls.
For buyers comparing this engine with newer electronically controlled diesel engines, its mechanical architecture can be an important distinction.
The combination of four-cylinder construction, compact displacement and 125 MHP output makes the 4JH3-DTE particularly relevant for pleasure craft where available engine-room space and engine weight must be considered alongside propulsion requirements.
Applications and Compatibility
The Yanmar 4JH3-DTE marine engine is designed for pleasure-boat propulsion and can be considered for compatible vessels requiring an inboard diesel engine in this output range.
Potential applications include suitable motorboats, cruising vessels and other pleasure craft, as well as repower projects replacing an older marine diesel engine.
When evaluating the 4JH3-DTE as a replacement engine, horsepower should not be the only consideration.
The existing marine gearbox, reduction ratio, engine mounts, shaft arrangement, propeller, exhaust system, cooling arrangement and available engine-room space should all be evaluated.
This becomes particularly important when replacing an engine from another manufacturer. Two engines with similar horsepower can have substantially different dimensions, mounting positions and driveline requirements.
Yanmar supports the 4JH3-DTE with compatible Kanzaki and ZF shaft-drive gear options, providing different possibilities according to the required propulsion installation.
Customers comparing alternative power ratings can also browse our Yanmar diesel engines range and related marine inboard engines for other suitable propulsion options.
Engine Design and Performance
The 4JH3-DTE uses an inline four-cylinder, four-stroke diesel configuration with a total displacement of 1.995 litres (approximately 122 cu in).
Its cylinders have an 84 × 90 mm bore and stroke, providing the internal dimensions for the engine’s compact displacement.
Maximum output is specified at 91.9 kW / 125 MHP at 3,800 rpm under the applicable Yanmar rating conditions.
The engine is turbocharged and intercooled.
Turbocharging increases the quantity of air available to the engine, while the intercooler reduces the temperature of the compressed intake air before combustion.
Fuel delivery uses a direct-injection system with a Bosch distributor-type VE pump. The engine employs mechanical controls rather than an electronic common-rail system.
This combination provides a distinctly mechanical marine diesel architecture that can be particularly relevant to buyers replacing older propulsion equipment.
Cooling and Electrical System
The Yanmar 4JH3-DTE uses a freshwater cooling system.
Engine coolant is circulated by a centrifugal freshwater pump, while the seawater side uses a rubber-impeller seawater pump to remove heat from the system.
This arrangement keeps the engine’s internal cooling circuit separated from the raw seawater circuit.
For marine installations, the complete cooling system—including seawater intake, hoses, exhaust mixing arrangement and associated components—should be inspected and correctly matched during installation.
The engine also uses a 12V electric starting system.
Yanmar’s current specification lists a 12V, 125A alternator, providing another important consideration when integrating the engine with the vessel’s electrical system.
Compact Inboard Installation
Size and weight can be critical when choosing an inboard marine engine, particularly for repower projects.
Yanmar specifies a dry engine weight of approximately 229 kg (504.8 lb) without marine gear.
This figure should be distinguished from the installed weight of a complete propulsion package because the selected gearbox and other equipment will increase total weight.
For a configuration fitted with the KM4A2 marine gear, Yanmar publishes dimensions of approximately 1001.3 mm long, 581 mm wide and 661 mm high.
Dimensions can change depending on the marine gear and exhaust elbow selected.
This is particularly important when assessing the engine for a repower. Buyers should therefore use the dimensions of the exact engine-and-gear configuration being purchased rather than assuming that every 4JH3-DTE package has identical external dimensions.
Who Is This Engine Suitable For?
The Yanmar 4JH3-DTE is particularly relevant to buyers requiring a compact 125 MHP marine diesel engine for a compatible pleasure craft.
Potential buyers include boat owners, marine workshops, boatbuilders, engineers and repower specialists seeking a four-cylinder Yanmar inboard engine with mechanical controls and direct fuel injection.
Its 1.995-litre displacement and 229 kg dry engine weight can make it particularly attractive where installation space and weight are important considerations.
For owners replacing an existing engine, the 4JH3-DTE should be evaluated against the complete propulsion system rather than horsepower alone.
Engine-room clearance, marine gear, reduction ratio, shaft and propeller requirements, engine mounts, cooling, exhaust and electrical connections should all be confirmed before purchase.
Technical Specifications
For buyers who need the essential information quickly, the principal Yanmar 4JH3-DTE 125HP specifications are summarized below.
| Specification | Details |
|---|---|
| Manufacturer | Yanmar |
| Model | 4JH3-DTE |
| Product Type | Marine inboard diesel engine |
| Configuration | Inline 4-cylinder, 4-stroke, water-cooled diesel |
| Rated Output | 91.9 kW / 125 MHP |
| Rated Speed | 3,800 rpm |
| Displacement | 1.995 L (122 cu in) |
| Bore × Stroke | 84 × 90 mm (3.31 × 3.54 in) |
| Aspiration | Turbocharged & Intercooled |
| Fuel System | Direct injection, Bosch distributor-type VE pump |
| Engine Controls | Mechanical |
| Cooling System | Freshwater cooling with seawater circuit |
| Starting System | Electric, 12V |
| Alternator | 12V – 125A |
| Dry Weight Without Gear | 229 kg (504.8 lb) |
| Dimensions* | 1001.3 × 581 × 661 mm |
| Crankshaft Rotation | Counterclockwise viewed from stern |
| Certifications | RCD 1, BSO II, EMC, SOLAS |
| Primary Application | Pleasure-boat marine propulsion |
Published dimensions include the KM4A2 marine gear and can vary with different gears or exhaust elbows.
Ordering and Support
Before ordering the Yanmar 4JH3-DTE 125HP Diesel Marine Inboard Engine, buyers should confirm the exact engine configuration and determine whether it is compatible with their vessel.
For a repower, useful information includes the existing engine model, marine gearbox, reduction ratio, propeller specification and available engine-room dimensions.
The 4JH3-DTE can be paired with compatible marine gear configurations, so the gearbox included with a particular engine should be confirmed before purchase rather than assuming a standard transmission is supplied with every unit.
Customers looking for other power outputs can explore our Yanmar diesel engines collection, related marine inboard engines and compatible propulsion equipment.
For current availability, included equipment and configuration information, contact JB Marine GmbH with your vessel and engine requirements.
Frequently Asked Questions
How much power does the Yanmar 4JH3-DTE produce?
The Yanmar 4JH3-DTE is rated at 91.9 kW / 125 MHP at 3,800 rpm under Yanmar’s specified rating conditions. It uses a four-cylinder, 1.995-litre diesel configuration with turbocharging and intercooling.
What is the displacement of the Yanmar 4JH3-DTE?
The engine has a displacement of 1.995 litres (approximately 122 cu in). It uses four inline cylinders with an 84 mm bore and 90 mm stroke, creating a compact engine platform for compatible pleasure-boat propulsion installations.
Is the Yanmar 4JH3-DTE turbocharged?
Yes. The 4JH3-DTE is turbocharged and intercooled. Turbocharging increases the intake-air supply, while intercooling manages the temperature of the compressed air before it enters the engine.
Does the 4JH3-DTE use common-rail injection?
No. The engine uses direct fuel injection with a Bosch distributor-type VE pump and mechanical controls. Buyers should therefore distinguish the 4JH3-DTE from newer electronically controlled common-rail Yanmar marine engines.
How much does the Yanmar 4JH3-DTE weigh?
Yanmar specifies a dry weight of approximately 229 kg (504.8 lb) without marine gear. The complete propulsion package will weigh more once the selected gearbox and associated installation equipment are included.
What are the dimensions of the Yanmar 4JH3-DTE?
Yanmar publishes dimensions of approximately 1001.3 × 581 × 661 mm for the configuration including a KM4A2 marine gear. Dimensions can vary with different gearbox and exhaust-elbow configurations, so the exact package should be checked before installation.
Can the Yanmar 4JH3-DTE be used for a repower?
The engine can be considered for a compatible marine repower. Suitability depends on available engine-room space, gearbox and reduction ratio, engine mounts, shaft and propeller configuration, cooling, exhaust and electrical requirements rather than the 125 MHP rating alone.
