The ARCO 60050 Alternator fits late model Mercruiser 12 Volt, 55 Amp applications. Internal regulator, 2" mounting foot, and single-groove serpentine pulley included. It replaces the following part numbers: Marine Power 1210-000, Mercury 12449, Mercury 78403A1, Mercury 78403A2, Mercury 817119A1, Mercury 817119A4, Mercury 92497A3, Mercury 98555, Mercury 98555A1, Sierra 18-5957, and Sierra 18-5966. All alternators are engineered for performance and reliability. All alternators are engineered and manufactured with precision and quality. All alternators must meet or exceed OEM performance before being boxed.