ARCO 12V 55A Single-Groove Marine Alternator

The ARCO replacement alternator is built for late-model MerCruiser charging systems that use a single-groove pulley and the specified marine mounting foot. It uses an internal regulator, so the regulation function is contained in the alternator rather than handled by a separate external unit. The supplied pulley keeps the replacement focused on the original belt arrangement instead of requiring the customer to source that part separately. It is a direct-service option for a broad group of MerCruiser and Marine Power cross references listed by the manufacturer.

ARCO states that its marine alternators are engineered for reliability, manufactured to precise quality standards, and checked against OEM performance requirements before packaging. That quality-control approach is particularly important on a replacement charging component that has to operate in heat, vibration, and a corrosive engine-compartment environment. The cross-reference list includes Mercury 12449, 78403A1, 78403A2, 817119A1, 817119A4, 92497A3, 98555, and 98555A1, along with Marine Power 1210-000. Sierra 18-5957 and 18-5966 are also listed as interchange references.

For installation, the existing belt alignment, pulley position, mounting geometry, and cable connections should be compared with the removed alternator before the new unit is tightened into place. Clean electrical connections help reduce resistance and support proper charging performance after installation. ARCO lists a 12-month warranty against defects in materials and workmanship for leisure use and 90 days for commercial or racing use. The source also notes that eligible rotating-electric products can receive an extra year of warranty when registered within 30 days of purchase.

• Internal regulator with supplied single-groove pulley
• Marine mounting geometry for the specified MerCruiser applications
• Cross-references multiple Mercury, Marine Power, and Sierra part numbers
• ARCO tests alternators against OEM performance requirements before boxing

For charging-system replacements that share the same marine installation requirements, Browse more Marine Alternators for related replacement and service components.