1 3

12V 275A Externally Regulated, Isolated Ground, 49mm K6 Pulley [PN#'s 4021 & 4023]

12V 275A Externally Regulated, Isolated Ground, 49mm K6 Pulley [PN#'s 4021 & 4023]

ARC4021

$1,096.70 USD
$1,096.70 USD
Sale Sold out
Shipping calculated at checkout.
! This alternator comes in two different mounting footprints so make sure to select the correct type in variants at the bottom of this section.
Mounting Configurations:

Model A (Dual Foot 3.15")
  • Mounting Style: 3.15-inch dual-foot saddle configuration
  • Terminal Placement: Rear-facing heavy-duty battery connection post
  • Common Compatibility: Directly fits standard Yanmar marine engine footprints

Model B (Dual Foot 4.00")
  • Mounting Style: 4.00-inch J180-style saddle configuration
  • Terminal Placement: Side-mounted battery connection post for tight clearance areas
  • Common Compatibility: Fits standard heavy-duty commercial marine and industrial engines
49mm K6 Pulley 

High-Output Marine Alternator (12V / 275A)
This heavy-duty alternator is engineered for high-demand marine and RV electrical systems. It provides exceptional charging performance at idle and low engine speeds. The unit features advanced electrical isolation and premium cooling to manage sustained high-amperage output safely.

We recommend getting the ZEUS OMEGA Regulator Kit to control and regulate your alternator for maximum charging efficiency.

Technical Performance
  • Amperage Output: 275 Amps maximum capability
  • System Voltage: 12 Volts nominal operation
  • Drive Configuration: 49mm K6 six-groove serpentine pulley
  • Shaft Diameter: 17mm heavy-duty drive shaft

Advanced Electrical Design
  • External Regulation: Requires an external smart regulator to optimize battery charging profiles.
  • Isolated Ground: Separates system negative from the engine block to eliminate stray current corrosion.
  • Hull Protection: Essential safely feature for aluminum, steel, and advanced composite vessels.

Specifications

Electrical Performance:
Nominal Voltage: 12 Volts
Maximum Output: 275 Amps
Ground Type: Isolated ground
Regulation: External regulation required

Mechanical Specs:
Drive Pulley: 49mm K6 serpentine
Shaft Diameter: 17mm
Cooling: Dual internal fans

Mounting Profiles:
Part #4021: 3.15-inch dual foot / rear battery post
Part #4023: 4.00-inch dual foot / side battery post

Installation Details

Safety Preparation:
1. Disconnect Batteries: Switch off all battery selectors and disconnect the negative cables.
Verify Fitment: Confirm the old alternator matches the new dual-foot spacing (3.15" or 4.00").
2. Physical Mounting
Align Foot: Slide the alternator into the mounting saddle on the engine bracket.
Insert Fasteners: Insert the main mounting bolt and the adjustment arm bolt finger-tight.
Check Alignment: Ensure the K6 pulley aligns perfectly with the engine crank pulley.
Torque Bolts: Tighten all mounting hardware to the engine manufacturer's torque specifications.
3. Wiring Connections
Positive Output: Connect the heavy-gauge B+ cable to the positive output terminal post.
Isolated Ground: Connect a dedicated heavy-gauge negative cable to the isolated ground terminal post.
Field Wire: Route the field wire from the external regulator to the alternator field terminal.
Stator/tach: Connect the tachometer or stator wire if your system utilizes an alternator-driven RPM gauge.
4. Belt Tensioning
Apply Tension: Pivot the alternator to tension the K6 serpentine belt.
Deflection Check: Ensure the belt deflects roughly 1/4 to 1/2 inch on its longest run.
Secure Arm: Tighten the adjustment arm bolt firmly to lock the tension.
5. Commissioning
Reconnect Power: Reattach the battery negative cables and turn on battery switches.
Program Regulator: Set the external regulator parameters to match your specific battery chemistry.
Engine Test: Start the engine and verify charging voltage with a digital multimeter.

Pelagic Power Tip

Mounting Footprint

Low stock: 2 left

View full details

Have a Question?