Arco
ARCO Alternator - 24V 4kW DF4 - Dual Foot 4" - Side Battery Post - Externally Regulated - Isolated Ground - 49mm K6 Pulley - 4403
£1,693.20
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4403
The ARCO Zeus A4000-24V LTO is a large-frame 24V high-output alternator tuned for Low Turn On, generating over 1.4kW as early as 1,500 RPM so it charges hard even at idle. It delivers up to 144 amps cold at 27.5V and a sustained 130 amps while cruising, replacing a noisy generator on marine and off-grid systems. This isolated-ground version uses a 4 inch J180 saddle mount and replaces most Volvo Penta 4 inch J180 alternators.
✓
Collection or delivery in 1-2 weeks
Pickup available at Mercury Yacht Harbour
Usually ready in 2-4 days
Description
The Zeus A4000-24V LTO is built for boats and off-grid systems that spend a lot of time at idle or low engine speed. Its Low Turn On design starts producing serious power just below 1,500 RPM, so it keeps large 24V banks charging while you manoeuvre, sit at anchor or run a slow cruise, work that would otherwise fall to a separate generator.
A native 24V rotor and field, a large 138mm stator and an E-coat finish let the A4000 hold its output without cooking. As with every Zeus alternator, ARCO measures the hot ratings the hard way, after a full hour at 3,000 RPM beneath a plexiglass heat shield rather than in cool ambient air, so the published cruising and idle figures reflect a hot engine bay rather than a laboratory.
It is externally regulated, so it needs a dedicated controller such as the ARCO Zeus Bluetooth regulator to manage charging and run lithium safely. This version is supplied with an isolated ground and a 4 inch J180 saddle mount, a direct replacement for most Volvo Penta 4 inch J180 alternators. It is SAE J1171 certified and made in the USA.
PRODUCT DETAILS
- Low Turn On design: over 1.4kW (51A) by about 1,500 RPM
- Native 24V large-frame alternator for fast bank charging
- Up to 144 A cold and 130 A sustained cruising at 27.5V
- Externally regulated (EX); pair with ARCO Zeus Bluetooth regulator
- Conservative hot ratings tested at 3,000 RPM under a heat shield
- Charges lithium (LiFePO4) and lead-acid banks with the right regulator
- 4 inch J180 saddle mount, isolated ground, replaces Volvo Penta J180
- Isolated ground for marine installations
- SAE J1171 certified and made in the USA
- ARCO Zeus A4000-24V LTO alternator
- External-regulation terminal block
- P-Type field harness
- Fitted 49K6 pulley (6-groove, 49mm)
- M17 x 1.5 x 24mm pulley nut
- 18mm ID x 29mm OD washer
No exploded diagram available for this product.
No compatible transducers listed for this product.
No spares or accessories listed for this product.
Key specifications
| Voltage | 24V |
| Max Output (Cold, 9,000 RPM) | 144 A at 27.5V (3,960 W, 5.7kW PTO) |
| Sustained Cruising Output (Hot, 6,000 RPM) | 130 A at 27.5V (3,575 W, 5.1kW PTO) |
| Sustained Idle Output (Hot, 3,000 RPM) | 108 A at 27.5V (2,970 W, 4.2kW PTO) |
| Regulation | External Only (EX) |
| Standard Pulley | 49K6 (6-groove, 49mm) |
Electrical
| Field Type | P |
| Rotor Poles | 16 |
| Rotator Source Voltage | 24V (native) |
| Stator Size | 138mm |
| Diodes | 6 positive, 6 negative, 50A rated, avalanche |
| Cut-In RPM | 1,072 alternator RPM |
| Maximum Alternator RPM | 19,000 |
| Max Continuous Operating Temperature | 100C (212F) |
Mechanical
| Frame Size | Large |
| Weight | 7.2 kg (15.89 lb), heaviest option (N62 clutch) |
| Finish | Black E-coating |
| Battery Post | M8 thread post, side mount |
| Pulley Mount | 17mm dia shaft, 25mm long, threaded M17 x 1.5 |
| Pulley Hardware | M17 x 1.5 x 24mm nut with 18mm ID x 29mm OD washer (included) |
Fitment
| Housing/Mount | 4 inch J180 saddle mount |
| Ground Type | Isolated ground |
| Application | Replaces most Volvo Penta 4 inch J180 installations |
Compliance
| Certification | SAE J1171 certified |
| Country of Origin | USA |
No videos available for this product.
Does this alternator include a regulator?
No. Every ARCO Zeus alternator is externally regulated (EX), so it has no built-in regulator and will not charge on its own. It needs a dedicated external regulator, and ARCO recommends the Zeus Bluetooth Alternator Regulator, which is designed to get the most from the alternator across 12V to 48V systems and is essential for safe lithium charging.
What does LTO (Low Turn On) mean?
LTO stands for Low Turn On. The A4000 is tuned to produce useful power at low engine speed, generating over 1.4kW (about 51 amps) by just under 1,500 RPM and around 2.4kW (87 amps) at 2,000 alternator RPM. That makes it a strong choice for engines that spend a lot of time at idle or low cruise, where it keeps charging hard without a separate generator.
What do the hot output figures mean?
ARCO publishes deliberately conservative hot ratings. Instead of testing in cool ambient air, it runs the alternator for a full hour at 3,000 RPM under a plexiglass heat shield, with the stator reaching around 305F, far harsher than the industry-standard 140F ambient test. The hot cruising and idle figures therefore reflect what you can expect in a hot engine bay rather than an optimistic bench number.
Which engines does this version fit?
This version has a 4 inch J180 saddle mount with an isolated ground and replaces most Volvo Penta 4 inch J180 alternators.
