OMC Alternator - 18-5951 S/S 18-5957 OMC Alternator - 18-5951 by Sierra. S/S 18-5957. Please use the Red PARTS CHARTS button (top of any page) to locate the correct part for your application. $ 125.13          Unavailable      More Information Mercruiser Alternator - 18-5951 - S/S 18-5957 Mercruiser Alternator - 18-5951 by Sierra. S/S to 18-5957. Please use the Red PARTS CHARTS button (top of any page) to locate the correct part for your application. $ 125.13          Unavailable      More Information