Mercury - Voltmeter 8-18V Electrical System Monitoring Black Face Chrome Bezel 79-8M6020009. OverviewThis 8-18V voltmeter gives you a steady look at how your electrical system is holding up while you're out on the water. The needle moves in a slow, even sweep, so dips and spikes stand out without getting mixed in with hull movement. It's the kind of gauge you check out of habit-quick glance, quick answer, and back to running the boat. Simple, clean, and built for everyday use.. Key Features • 8-