Sierra 18-5907, New Starter. Top mount rear entry starter for opposite rotation GM & Ford engine. Will also replace standard rotation (will not replace non-starter mounted solenoids). Mercruiser built 4 cylinder 165/170/180/190/470/485/488Replaces Mercury: 50-72550A2, 50-79604A3, & 50-97499A2, R4.OMC: 981289, 982202. Crusader: 42091