Galvanic Isolators

What Is a Galvanic Isolator and Why Does Your Boat Need One?

Any time a boat is plugged into a marina's AC shore power, it becomes part of a shared electrical network — and that network can quietly destroy your vessel from the water up. Galvanic isolators are a critical line of defense for any boat owner who regularly docks at a marina. A galvanic isolator is an electrical device designed to protect boats and marine equipment against galvanic corrosion by isolating the AC grounding system from the DC bonding system, preventing harmful electrical currents from flowing through the water and corroding underwater metals.

It blocks low-voltage DC currents that enter your boat via the shore power earth wire — currents that can cause corrosion to the boat's underwater metals, like the hull, propeller, shaft, and other submerged components. Over time, this kind of galvanic corrosion can eat through props, through-hull fittings, trim tabs, and outdrives, leading to expensive repairs or even dangerous structural failure.

How Galvanic Isolators Work

The function of a galvanic isolator is to provide AC continuity of the grounding conductor — required for safety in the event of an AC fault — while simultaneously blocking the flow of corrosion-causing galvanic current. Internally, the isolator consists of two diodes connected in anti-parallel fashion; connected this way, the diodes allow current in both directions but only above a certain threshold voltage of about 1.4 Vdc. This threshold is higher than typical galvanic voltages, so harmful corrosive current is stopped while safety ground continuity is maintained.

Today, ABYC standards require the use of fail-safe galvanic isolators, a design where the diodes fail closed rather than open — meaning you lose galvanic protection in the unlikely event of a failure, but you never lose the critical safety ground. Look for galvanic isolators certified to meet industry standards such as ABYC (American Boat and Yacht Council) and UL1500 (Underwriters Laboratories' Marine Ignition Protection), as these certifications ensure the isolator's reliability and performance.

What to Look for When Shopping Galvanic Isolators

• Amperage rating: Match the isolator's amp rating to your shore power connection — 30A for single 30-amp cords, 60A for 50-amp or dual 30-amp setups.
• Fail-safe design: Always choose a fail-safe model that meets current ABYC standards for maximum safety.
• Certifications: ABYC and UL1500 certifications validate real-world performance and safety compliance.
• Hull material: Aluminum-hull boats have additional considerations — the galvanic isolation device for these boats should provide around 2.5 volts of isolation to shield the boat from harmful DC and AC electrolytic voltages originating from the dock.
• Installation location: The isolator is located between the inlet and the main panel and should be installed by a qualified marine electrician.

Top Brands in Galvanic Isolators

NewMar is a respected name in marine DC power management, and their galvanic isolators reflect the same engineering rigor found across their entire product line. NewMar isolators are designed for reliable corrosion protection and are a trusted choice for serious boaters.

Quicksilver brings decades of marine expertise to their electrical accessories, offering galvanic isolators built to withstand demanding saltwater environments alongside their well-known line of marine engine components.

Pro Mariner is one of the most recognized names in marine shore power protection. The ProSafe FailSafe series of galvanic isolators prevents the most common forms of corrosion and premature zinc loss, and when installed on a boat connected to AC shore power, they interrupt galvanic current flow with other boats at a marina.