Engine
Engine 29HP — Yanmar 3YM30 wiring diagram
Original Yanmar 3YM30, distinct from 3YM30AE. Manufacturer service data specifies a 1.4 kW starter and 60 A internally regulated alternator (80 A optional). The 250 A cranking and 350 A surge are planning estimates; identify the fitted panel and charging equipment.
- Continuous draw
- 250 A
- Rated output
- 60 A
- Surge current
- 350 A
Wiring diagram
How the 3YM30 29HP 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
- 350 A
- Cranking current
- 250 A
- Voltage drop
- 1.9%
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
- 350 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. 0BYMM-G00100 \u2014 third edition, November 2006), checked 2026-10-01. Manufacturer documentation →
Engine and edition
This is the original 1.115 L 3YM30 covered by the 3YM30/3YM20/2YM15 service manual, not the later 3YM30AE. The standard alternator is the internally regulated Hitachi LR160-741, 12 V/60 A; the manual also documents an optional 80 A alternator. Identify the fitted alternator before using the charging estimate.
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 electrical chapter distinguishes the original instrument panel from a newer panel with a 3 A instrument fuse. The engine harness includes the starter relay, oil-pressure and coolant-temperature warnings, charge warning/excitation circuit and electric stop solenoid. Match the panel and harness drawing to the engine serial number; neither the warning lamp nor the stop wire is a charging output.
Checks and model limits
The Hitachi S114-817A starter is rated 1.4 kW. Its service test specifies 250 A at 8.4 V under a defined load; that is not a universal cranking current measured at a 12 V battery. The catalog 250 A starting draw and 350 A surge remain planning assumptions. Check actual cold cranking voltage, cable losses and the starter battery before relying on them. Keep the battery connected while the alternator runs; a lithium installation needs charge-current and disconnect coordination beyond this three-terminal model.
Source: manufacturer document — electrical diagrams printed pp. 183–185 (PDF 204–206), starter p. 186 (PDF 207), alternator pp. 189–192 (PDF 210–213). 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 3YM30 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
Original Yanmar 3YM30, distinct from 3YM30AE. Manufacturer service data specifies a 1.4 kW starter and 60 A internally regulated alternator (80 A optional). The 250 A cranking and 350 A surge are planning estimates; identify the fitted panel and charging equipment.
- Continuous draw
- 250 A
- Rated output
- 60 A
- Surge current
- 350 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.
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Plan your installation with 3YM30 29HP.
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