Mercury - Voltage Regulator Kit Electrical Charging System Marine-Grade Components 8M0084173. Overview. Every boater has had that moment - you turn the key, the engine fires, and you instantly know the electrical system is happy. There's a kind of quiet confidence in seeing your gauges settle where they should and knowing your battery is charging the way it's supposed to. The Mercury 8M0084173 Voltage Regulator helps deliver that peace of mind. It keeps your outboard's electrical system stable w