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The Fundamentals of Marine Isolation Transformers & Galvanic Isolators

Matervolt Transformer Marine isolation transformers and galvanic isolators may sound like technical jargon, but they play a crucial role in ensuring the safety of your boat's electrical systems. These devices help protect against electrical shock hazards and damage to onboard electronics caused by galvanic corrosion. In this article, we will dive into the science behind marine isolation transformers and galvanic isolators, how they work, and the different types available. We'll also cover some of the leading brands in the market, including Victron Energy, Pro Mariner, Hubbell, MasterVolt, Newmar, and Suncor. So, whether you're an experienced boater or just starting out on your nautical journey, read on to learn more about how these important devices can keep you safe and your boat running smoothly.

The Science Behind Isolation Transformers

Hubbell Transformer Isolation transformers are vital in ensuring electrical safety on boats and protecting sensitive electronics from shore power issues. They utilize galvanic isolation to separate shore power from onboard power, thereby eliminating stray AC currents and preventing galvanic corrosion of metal parts in the electrical system. Isolation transformers can be built using traditional transformers or toroidal transformers for isolation and are encased in solid epoxy resin to protect against seawater corrosion. Additionally, these transformers feature parallel wiring, which isolates AC power polarity from the shore installation, enhancing their safety and effectiveness in marina environments.

How To Ensure Clean and Stable AC Power

Newmar Transformer Isolation transformers play a crucial role in ensuring clean and stable AC power for onboard electronics. By filtering out electrical noise, these transformers provide a clean power source that protects sensitive electronics from voltage fluctuations. Additionally, isolation transformers offer soft start capabilities, preventing power surges that could potentially damage onboard systems. The kVA capacity of the transformer also determines the stability of the power it provides, with capacities ranging from 2.5 kW to 22 kW. Choosing a transformer with a higher kVA capacity is important for more stable power. Furthermore, isolation transformers are designed to operate at the correct hertz frequency, ensuring compatibility with onboard power systems.

How do Galvanic Isolators Work?

Galvanic isolators function by utilizing parallel wiring to block galvanic current from shore power. These isolators employ solid-state electronics to conduct or obstruct galvanic current while preserving electrical polarity to prevent galvanic corrosion onboard. Installation involves connecting the bulkhead enclosure and metal components of the electrical system. Galvanic isolators, which are suitable for small boats that spend considerable time in the water, are designed to operate at the appropriate hertz frequency for onboard power.

Types of Transformers & Isolators

Pro-Mariner Transformer Marine isolation transformers are crucial components on boats, as they prevent electric shock, reduce corrosion, and improve the performance of onboard electrical equipment. Galvanic isolators, on the other hand, protect boats from galvanic corrosion caused by a potential difference between metals in contact with seawater. Auto-transformers are commonly used to step up or down the voltage in a single-winding transformer. Isolation transformers, on the other hand, provide complete electrical isolation between the input and output circuits. Lastly, step-down transformers are used to reduce the voltage level of electrical power. These different types of transformers and isolators play vital roles in ensuring the safety and efficiency of onboard electrical systems.

The Hidden Danger of Stray Electric Current in Marinas

Coutesy of Victron Energy If you enjoy swimming in or near marinas, you may not be aware of a serious hazard that could put your life at risk: stray electric current. Stray electric current is the portion of an electric current that flows over a path other than the intended one, such as through the water. Stray electric current can cause injury or death to human beings swimming around boats, especially in freshwater.

How to Choose the Right Marine Isolation and Galvanic Transformer

When selecting a marine isolation and galvanic transformer for your boat, you need to consider several factors, such as:

Victron Energy

Victron Trnasformer Victron Energy specializes in high-quality electrical power solutions for boats, offering marine isolation transformers and galvanic isolators. These products ensure optimal performance and safety by providing complete electrical isolation, protecting against shock, and reducing corrosion. Victron Energy provides reliable and efficient power solutions for boats of different sizes and electrical needs. Their isolation transformers, operating at 50 or 60 Hz frequencies, effectively separate AC power from the DC system, preventing issues and interference.

Pro Mariner

Pro Mariner is a well-known brand that offers marine isolation transformers and galvanic isolators for boats and yachts. These devices ensure safety on the water by preventing electric shock hazards and galvanic corrosion. Pro Mariner's products provide clean and stable AC power, protecting against electrical damage and safety hazards.


Hubbell is a trusted marine brand known for reliable isolation transformers and galvanic isolators, crucial for ensuring electrical safety on boats. Isolation transformers use a metallic case to block dangerous currents, preventing hum and protecting the onboard system from shore power. Galvanic isolators disconnect conductors, averting galvanic corrosion between metal boat components. Hubbell's products are durable, designed for marine environments, providing peace of mind to boat owners.


The Mastervolt GI 7 is a lightweight isolation transformer weighing 22 lb. (10 kg), offering compactness and convenience without sacrificing performance. These transformers are crucial safety devices for boats, protecting against electrical faults and galvanic corrosion. When used with galvanic isolators, they safeguard vessels by separating AC shore power and DC onboard systems, ensuring safety for both the boat and its occupants. Mastervolt, a leading brand, provides reliable and lightweight solutions for marine isolation transformers and galvanic isolators.


Newmar Transformer Newmar offers reliable marine isolation transformers for protection against electrical shock and interference. These transformers are durable and protected from external factors with a metallic case. They safely contain loose conductors, preventing accidental contact. Designed for DC power at various frequencies, Newmar is a trusted name in the industry for high-quality marine isolation transformers.


Suncor marine isolation transformers are crucial for boat and yacht safety. They provide electrical isolation, protection, and stability. Suncor is a leading manufacturer of high-quality marine isolation transformers that use state-of-the-art technology to ensure reliability and efficiency at sea.

Frequently Asked Questions

Do I need an isolation transformer for my boat?

If your boat is equipped with a shore power connection, it is highly recommended to have an isolation transformer. This essential device protects your boat's electrical system from stray currents and voltage fluctuations, minimizing the risk of galvanic corrosion on metal parts. By creating an onboard power source, an isolation transformer greatly enhances the safety of those on your boat or swimming nearby. Consult with a marine electrician to determine the appropriate size and type of isolation transformer for your boat.

Where does a galvanic isolator need to be installed?

A galvanic isolator should be installed in-line between the shore power inlet and the boat's AC panel to ensure proper protection. It should be mounted vertically, away from heat sources, and as close to the shore power inlet as possible. Additionally, a ground wire should be connected to the on-board bonding circuit to prevent corrosion and damage to electronics. Remember that proper grounding and installation by a qualified electrician are essential.

Are marine isolation transformers and galvanic isolators crucial for my boat's safety?

Marine isolation transformers and galvanic isolators are essential for ensuring the safety of your boat. Installing both of these devices is highly recommended to provide maximum protection. They work together to prevent electrical hazards and protect your boat's electrical system from potential damage.

If you have additional questions, please don't hesitate to contact our product experts at (800) 426-6930.