Mercury - Voltage Regulator/Rectifier FourStroke 30-60 HP Series Marine-Grade Composite & Stainless Steel 893640T01. Overview. There's a certain peace that settles in when your electrical system is steady and predictable. You feel it the moment your gauges stay bright, your electronics hold their charge, and your engine fires up without hesitation. A good voltage regulator isn't something most boaters think about, but when it's doing its job right, the whole boat just feels calmer and more depen