Engine
Engine 50HP — Yanmar 4JH2E wiring diagram
Naturally aspirated Yanmar 4JH2E with original 1.4 kW starter and 55 A Hitachi internally regulated alternator; 80 A alternator documented as an option. Modeled 180 A cranking and 360 A surge are estimates, separate from starter output power.
- Continuous draw
- 180 A
- Rated output
- 55 A
- Surge current
- 360 A
Wiring diagram
How the 4JH2E 50HP is wired.
Open this example in Crimp to use your own parts and cable lengths. Review the assumptions and installation notes as you adapt the circuit.
Cable sizing for this example
Use the diagram as a starting point for your installation. Replace the example equipment and cable lengths with your own, and check the connections against your exact model's instructions.
3 m one way
12 V system
- Wire
- 120 mm² · 4/0 AWG
- Example fuse
- 250 A
- Cranking current
- 180 A
- Voltage drop
- 1.3%
Sized against ABYC E-11. The cranking current is what the starter draws. ABYC E-11 doesn't require a fuse on a cranking-motor conductor, so the fuse shown is the usual cranking-rated (Class T) choice, sized to hold the crank without nuisance tripping — it isn't there to protect the wire. The length is one way; voltage drop includes an equal-length return.
Run-length and manufacturer assumptions
The editable example uses 3.048 m (10 ft) runs unless a shorter run is stated. Metric overviews round these to 3 m. Adapt the parts and lengths to your installation before choosing cable and protection.
Supporting parts
- 6.1 m total of 120 mm² (4/0 AWG) marine cable
- Terminations for 120 mm² cable, matched to the equipment's screw terminals, leads or studs
- 250 A cranking-rated (Class T) fuse at the battery
- Heat-shrink, strain relief and terminal boots sized to the cable
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
Installation notes
Before you install.
Open a question for model-specific guidance and sources.
Verified against the manufacturer's documentation (rev. Service-manual compilation; individual sheets carry revision codes), checked 2026-10-01. Manufacturer documentation →
Engine and edition
The 4JH2E is the naturally aspirated member of the 4JH2 family. Do not substitute the turbocharged TE, HTE, DTE or UTE ratings. The original construction table specifies a 12 V, 1.4 kW starter and a 55 A internally regulated alternator. The electrical chapter identifies the standard alternator as Hitachi LR155-20 and separately documents an optional 80 A unit.
What the terminals mean
`Starter` represents the high-current starter supply, `Alt B+` the alternator charging output, and `Block GND` the intended negative return on an earth-return installation. They are functional drawing ports, not three interchangeable physical studs. Trace any factory link between alternator B+ and the starter battery stud before changing it; do not duplicate or remove that link without accounting for the original harness.
Controls and protection
The manufacturer wiring drawings distinguish the battery/starter circuit from the instrument harness, charge-warning/excitation connection, oil-pressure switch, temperature warning and stop arrangement. Preserve these circuits when adding house-bank charging. Never apply battery current to a sender or alternator warning terminal. Confirm the panel variant and installed alternator rather than selecting a drawing solely from engine horsepower.
Checks and model limits
The original battery section specifies a 12 V, 120 Ah starting battery and gives cable guidance for its stated installation conditions. This is not permission to use any 120 Ah house battery as a starter battery. The catalog 180 A cranking and 360 A surge remain estimates; starter output in kW is not its battery input consumption. Battery switching must retain an alternator load while running. Fuse selection for an altered charging run still depends on its cable and source fault current.
Source: manufacturer document — construction printed p. 1-6 (PDF 12), wiring pp. 9-1–9-5 (PDF 312–316), battery p. 9-7 (PDF 318), alternator p. 9-26 (PDF 337). Legacy copies hosted outside the manufacturer site are manufacturer-authored archive documents; the review date does not make them current installation instructions.
Fit check
Connect it to the rest of your system.
Describe your setup to draft a system with 4JH2E connected. Review the selected parts and cable lengths, then edit the diagram in Crimp.
The model only picks parts and draws the connections. Every wire size and fuse rating still comes from Crimp's own sizing, never from the model.
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Technical reference
Specifications and terminal map.
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Catalog specification
Naturally aspirated Yanmar 4JH2E with original 1.4 kW starter and 55 A Hitachi internally regulated alternator; 80 A alternator documented as an option. Modeled 180 A cranking and 360 A surge are estimates, separate from starter output power.
- Continuous draw
- 180 A
- Rated output
- 55 A
- Surge current
- 360 A
Terminal map
Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.
Starter
positive · input
Alt B+
positive · output
Block GND
ground · bidi
Sources and sizing method
Equipment specifications. Model details, ratings and terminal roles come from the catalog. Check your unit’s label and current manufacturer documentation for its exact revision.
Example sizing. Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. Results use the example current and run length shown above. Set your actual equipment, lengths and installation conditions in Crimp before choosing hardware.
Read how the sizing worksNext step
Plan your installation with 4JH2E 50HP.
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