At some point, most of us will have to replace an alternator on our boat. Selecting the proper alternator is critical for maintaining reliability. The proper amperage, pulley configuration, wiring harness, and mounting set up are all factors when selecting a new alternator. Most importantly, using a marine alternator for spark protection with a certification of SAE J1171 should ALWAYS be used. Never use an Alternator without that certification. We carry these marine specific alternators for your Mercruiser Sterndrive.