Engine
Engine 23HP — Volvo Penta MD11C wiring diagram
Volvo Penta MD11C with original 12 V / 1.5 kW starter and 35 A alternator. Modeled 110 A cranking and 220 A surge are estimates. The engine fusebox protects controls; the drawing omits the panel, excitation and stop circuits.
- Continuous draw
- 110 A
- Rated output
- 35 A
- Surge current
- 220 A
Wiring diagram
How the MD11C 23HP 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
- 110 A
- Voltage drop
- 0.8%
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. Publication 3167 \u2014 July 1976), checked 2026-10-01. Manufacturer documentation →
Engine and edition
The Volvo instruction book covers MD11C and its 110S installation, together with the sister engine. The original electrical table gives 12 V, a 1.5 kW starter and 35 A/420 W alternator. Its column labels transpose the current/power units; 35 A and 420 W are the physically consistent reading. Identify any replacement alternator before assuming this stock output.
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 diagram shows the starter battery cable, alternator B+ charging lead, engine fusebox and separate key-switch, charge-warning, oil-pressure and temperature-gauge connections. The fusebox is on the control branch. Moving its connection to a spare fuse contact does not add protection to the full-current starter cable. Keep the existing charging/excitation circuit intact when adding a second battery bank.
Checks and model limits
Stop the engine before opening its battery switch. Volvo explicitly prohibits switching charging circuits while the engine runs and requires the ordinary battery to remain connected during an assisted start. The catalog 110 A cranking and 220 A surge values remain estimates, not measured values from the manual. Stock charging is modeled at 35 A; update this if a different alternator is actually fitted. The diagram omits the panel harness, senders, engine stop control and any charging distributor, so it cannot establish the installation’s complete protection or alarm coverage.
Source: manufacturer document — electrical precautions printed pp. 17–18 (PDF 19–20), specifications pp. 27–28 (PDF 29–30), wiring p. 29 (PDF 31). 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 MD11C 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
Volvo Penta MD11C with original 12 V / 1.5 kW starter and 35 A alternator. Modeled 110 A cranking and 220 A surge are estimates. The engine fusebox protects controls; the drawing omits the panel, excitation and stop circuits.
- Continuous draw
- 110 A
- Rated output
- 35 A
- Surge current
- 220 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 MD11C 23HP.
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