Mercury - Quicksilver 828507Q5 Alternator Belt Mercury 3.0L V6 OptiMax Outboards (Non-Pro Models) 828507Q5. Overview. When your alternator belt slips or starts squealing, it's a sign it's done its time. The Quicksilver 828507Q5 Alternator Belt is the factory replacement for Mercury 3.0L V6 OptiMax outboards (non-Pro models, serial 1B227000 and up). It's the same belt Mercury installs on new motors-made to handle big power and constant RPM changes without stretching or glazing.. This belt keeps y