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ARCO Zeus A275/4300W-12V (A275L) High Output Alternator, 3.15"R Saddle Mount, Rear Exit B+, External Only, Isolated Ground (4021)
Model: 4021 · SKU: 4021
Prepared Nov 12, 2026
Common specifications
| Rated output current | |
|---|---|
| Sustained output current | 198 ASource [2, 3] |
| System voltage | 12 VSource [2, 3] |
| Rotation | Not documented |
| Ground type | Isolated GroundSource [2] |
| Mounting | 3.15”R Saddle Mount, Rear Exit B+Source [2] |
| Pulley | 49mm K6 (6 groove)Source [2] |
| Cut-in speed (RPM) | 1,061 RPMSource [3] |
| Maximum speed (RPM) | 19,000 RPMSource [3] |
| Stator size | |
| Regulator included | External OnlySource [2, 3] |
| Cooling | Dual cooling fansSource [2, 3] |
| Efficiency | Not documented |
| Operating temperature | 110 M °CSource [3] |
| Weight | |
| Dimensions | Not documented |
| Enclosure volume | Not documented |
| Warranty term | Not documented |
All recorded specifications
| Cooling | Dual cooling fansDocumented claim ConditionsPrinted as "Dual cooling fans" on ARCO's product page and "Dual Cooling fans" in the brochure's High Output Alternators list, which covers every Zeus high output alternator. Location: Product page description, "Coolest operating temperatures" list; brochure, High Output Alternators list Printed as "Dual cooling fans" on ARCO's product page and "Dual Cooling fans" in the brochure's High Output Alternators list, which covers every Zeus high output alternator. Location: Product page description, "Coolest operating temperatures" list; brochure, High Output Alternators list Official product page · ARCO Marine product page: ARCO Zeus A275/4300W-12V (A275L) High Output Alternator (arcomarine.com, October 27, 2026 capture)Official document · ARCO Zeus High Energy Collection brochure: Bluetooth Alternator Regulator & High Output Alternators (v2, arcomarine.com, October 27, 2026 capture) [2, 3] |
|---|---|
| Cut-in speed (RPM) | 1,061 RPMDocumented claim ConditionsPrinted as "Cut-In RPM 1,061 Alternator RPM" in the A275L-12V product page's Technical Specifications, which cover every part number of the page. Location: Product page, Technical Specifications, Cut-In RPM row Printed as "Cut-In RPM 1,061 Alternator RPM" in the A275L-12V product page's Technical Specifications, which cover every part number of the page. Location: Product page, Technical Specifications, Cut-In RPM row |
| Ground type | Isolated GroundDocumented claim ConditionsPrinted in the Ground Type column of the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021". Location: Brochure, A275L-12V DETAILS table, Ground Type column for part 4021 Printed in the Ground Type column of the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021". Location: Brochure, A275L-12V DETAILS table, Ground Type column for part 4021 |
| Maximum speed (RPM) | 19,000 RPMDocumented claim ConditionsPrinted as "Maximum Alt RPM 19,000" in the A275L-12V product page's Technical Specifications. Location: Product page, Technical Specifications, Maximum Alt RPM row Printed as "Maximum Alt RPM 19,000" in the A275L-12V product page's Technical Specifications. Location: Product page, Technical Specifications, Maximum Alt RPM row |
| Mounting | 3.15”R Saddle Mount, Rear Exit B+Documented claim ConditionsThe housing (mount) ARCO's brochure prints for part 4021, row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021"; ground type Isolated Ground, pulley 49mm K6 (6 groove). Location: Brochure, A275L-12V DETAILS table, Housing column for part 4021 The housing (mount) ARCO's brochure prints for part 4021, row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021"; ground type Isolated Ground, pulley 49mm K6 (6 groove). Location: Brochure, A275L-12V DETAILS table, Housing column for part 4021 |
| Operating temperature | 110 M °CDocumented claim ConditionsPrinted as "Max Continuous Operating Temperature 110°C" with its Fahrenheit figure in the product page's Technical Specifications; ARCO prints a maximum continuous operating temperature only, no lower limit. Location: Product page, Technical Specifications, Max Continuous Operating Temperature row Printed as "Max Continuous Operating Temperature 110°C" with its Fahrenheit figure in the product page's Technical Specifications; ARCO prints a maximum continuous operating temperature only, no lower limit. Location: Product page, Technical Specifications, Max Continuous Operating Temperature row |
| Pulley | 49mm K6 (6 groove)Documented claim ConditionsPrinted in the Pulley column of the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021". Location: Brochure, A275L-12V DETAILS table, Pulley column for part 4021 Printed in the Pulley column of the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021". Location: Brochure, A275L-12V DETAILS table, Pulley column for part 4021 |
| Rated output current | 310 ANeeds confirmationARCO's brochure prints 310 A for part 4021; its product page prints "Max Output (Cold, 9,000 RPM) 311 Amps". Neither names a revision that supersedes the other. ConditionsThe maximum output current ARCO's brochure prints for part 4021: A275L-12V DETAILS table row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021" (Maximum Output column 310), the cold figure at 9,000 alternator RPM. The product page's Technical Specifications print "Max Output (Cold, 9,000 RPM) 311 Amps", kept as the alternative. The product page prints "Sustained Cruising Output (Hot, 6,000 RPM) 227 Amps" and "Sustained Idle Output (Hot, 3,000 RPM) 198 Amps". ARCO says "cold" testing was done at 71 °F and measures "hot" output after 60 minutes at 3,000 RPM under a plexiglass shield. Location: Brochure, A275L-12V DETAILS table, row for part 4021 The maximum output current ARCO's brochure prints for part 4021: A275L-12V DETAILS table row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021" (Maximum Output column 310), the cold figure at 9,000 alternator RPM. The product page's Technical Specifications print "Max Output (Cold, 9,000 RPM) 311 Amps", kept as the alternative. The product page prints "Sustained Cruising Output (Hot, 6,000 RPM) 227 Amps" and "Sustained Idle Output (Hot, 3,000 RPM) 198 Amps". ARCO says "cold" testing was done at 71 °F and measures "hot" output after 60 minutes at 3,000 RPM under a plexiglass shield. Location: Brochure, A275L-12V DETAILS table, row for part 4021 |
| Regulator included | External OnlyDocumented claim ConditionsARCO's brochure prints the regulation of part 4021 as "External Only" (row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021"). The product page explains: "These units will come with a terminal block and a P-Type harness. They will only work with an external regulator". A regulator is not part of an External Only unit; ARCO names its Zeus Bluetooth regulator for these. Location: Brochure, A275L-12V DETAILS table, Regulation column for part 4021; product page, Regulation notes ARCO's brochure prints the regulation of part 4021 as "External Only" (row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021"). The product page explains: "These units will come with a terminal block and a P-Type harness. They will only work with an external regulator". A regulator is not part of an External Only unit; ARCO names its Zeus Bluetooth regulator for these. Location: Brochure, A275L-12V DETAILS table, Regulation column for part 4021; product page, Regulation notes Official document · ARCO Zeus High Energy Collection brochure: Bluetooth Alternator Regulator & High Output Alternators (v2, arcomarine.com, October 27, 2026 capture)Official product page · ARCO Marine product page: ARCO Zeus A275/4300W-12V (A275L) High Output Alternator (arcomarine.com, October 27, 2026 capture) [2, 3] |
| Stator size | 138 mm5.43 in convertedDocumented claim ConditionsPrinted as "Stator Size 138mm" in the A275L-12V product page's Technical Specifications. Location: Product page, Technical Specifications, Stator Size row Printed as "Stator Size 138mm" in the A275L-12V product page's Technical Specifications. Location: Product page, Technical Specifications, Stator Size row |
| Sustained output current | 198 ADocumented claim ConditionsThe sustained idle output ARCO prints for part 4021: the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021" (Sustained Idle Output column 198; its footnote reads "*3,000 alternator RPM sustained under load and hot conditions for 1 hour.") and the product page's "Sustained Idle Output (Hot, 3,000 RPM) 198 Amps". The page also prints "Sustained Cruising Output (Hot, 6,000 RPM) 227 Amps". ARCO measures "hot" output after the alternator has run 60 minutes at 3,000 RPM under a plexiglass shield. Location: Brochure, A275L-12V DETAILS table, Sustained Idle Output column for part 4021; product page, Technical Specifications, Sustained Idle Output row The sustained idle output ARCO prints for part 4021: the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021" (Sustained Idle Output column 198; its footnote reads "*3,000 alternator RPM sustained under load and hot conditions for 1 hour.") and the product page's "Sustained Idle Output (Hot, 3,000 RPM) 198 Amps". The page also prints "Sustained Cruising Output (Hot, 6,000 RPM) 227 Amps". ARCO measures "hot" output after the alternator has run 60 minutes at 3,000 RPM under a plexiglass shield. Location: Brochure, A275L-12V DETAILS table, Sustained Idle Output column for part 4021; product page, Technical Specifications, Sustained Idle Output row Official document · ARCO Zeus High Energy Collection brochure: Bluetooth Alternator Regulator & High Output Alternators (v2, arcomarine.com, October 27, 2026 capture)Official product page · ARCO Marine product page: ARCO Zeus A275/4300W-12V (A275L) High Output Alternator (arcomarine.com, October 27, 2026 capture) [2, 3] |
| System voltage | 12 VDocumented claim ConditionsPrinted as "Voltage 12V" in the product page's Technical Specifications and as the Voltage column of the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021". Location: Brochure, A275L-12V DETAILS table, Voltage column; product page, Technical Specifications, Voltage row Printed as "Voltage 12V" in the product page's Technical Specifications and as the Voltage column of the brochure row "12V 310 198 3.15”R Saddle Mount, Rear Exit B+ External Only Isolated Ground 49mm K6 (6 groove) 4021". Location: Brochure, A275L-12V DETAILS table, Voltage column; product page, Technical Specifications, Voltage row Official document · ARCO Zeus High Energy Collection brochure: Bluetooth Alternator Regulator & High Output Alternators (v2, arcomarine.com, October 27, 2026 capture)Official product page · ARCO Marine product page: ARCO Zeus A275/4300W-12V (A275L) High Output Alternator (arcomarine.com, October 27, 2026 capture) [2, 3] |
| Weight | 6.7 kg15 lb convertedNeeds confirmationARCO's A275L product page prints "Weight 14.9 lbs / 6.7 kg"; the brochure's Specifications table prints "12 lbs / 5.4 kg" in its A275L-12V column. ARCO's installation manual prints no weight, and neither document names a revision that supersedes the other. ConditionsPrinted as "Weight 14.9 lbs / 6.7 kg" in the A275L product page's Technical Specifications, for every A275L part. Location: Product page, Technical Specifications, Weight row Printed as "Weight 14.9 lbs / 6.7 kg" in the A275L product page's Technical Specifications, for every A275L part. Location: Product page, Technical Specifications, Weight row |
Warranty
Certificate records
No records documented.
Sources and revisions
- ARCO Zeus Alternator Installation Guide 2025 (TECH-001 REV-B 8/18/25, arcomarine.com, October 29, 2026 capture)Official installation manual · Revision TECH-001 REV-B · 2025-08-18 · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/TECH-001_ARCO_Zeus_Alternator_Installation_Guide_2025.pdf?v=1755639945
- ARCO Zeus High Energy Collection brochure: Bluetooth Alternator Regulator & High Output Alternators (v2, arcomarine.com, October 27, 2026 capture)Official document · Revision 1001 Cat 1 Rev A · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/The_ARCO_Zeus_Collection_Brochure_v2_488a3d13-7f71-461e-8999-4f88397839fc.pdf?v=1762453970
- ARCO Marine product page: ARCO Zeus A275/4300W-12V (A275L) High Output Alternator (arcomarine.com, October 27, 2026 capture)Official product page · Checked https://arcomarine.com/products/arco-zeus-a275l
- ARCO Zeus High Output Alternator Wiring Connection Instructions (TECH001 - REV001 7/31/25, arcomarine.com, October 29, 2026 capture)Official document · Revision TECH001 - REV001 · 2025-07-31 · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/ARCO_Zeus_Alternator_insert_2025_V3.pdf?v=1754409647
- ARCO Zeus Alternator & Regulator OEM Troubleshooting Guide (TECH-002 REV-A 7/31/25, arcomarine.com, October 29, 2026 capture)Official instruction manual · Revision TECH-002 REV-A · 2025-07-31 · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/TECH-002_ARCO_Zeus_Alternator_Regulator_OEM_Troubleshooting_Guide.pdf?v=1755639958
- ARCO Zeus Installation Audit v1.0 (TECH-004 REV-A 7/31/2025, arcomarine.com, October 29, 2026 capture)Official instruction manual · Revision TECH-004 REV-A · 2025-07-31 · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/TECH-004_ARCO_Zeus_Installation_Audit_v1.0.pdf?v=1755639979
- ARCO Zeus High Energy Collection brochure (file The_ARCO_Zeus_Collection_Brochure.pdf, arcomarine.com, October 29, 2026 capture)Official document · Revision 1001 Cat 1 Rev A · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/The_ARCO_Zeus_Collection_Brochure.pdf?v=1743020364
- High Output Alternator Performance Testing (ARCO Marine, "Updated: 5/10/2024", arcomarine.com, October 29, 2026 capture)Official document · Checked https://cdn.shopify.com/s/files/1/0110/9521/2098/files/ARCO_Zeus_High_Output_Alternator_Testing_Results_93023fc1-b11e-4181-9ad0-8b24e3e4ccca.pdf?v=1729633064.pdf