Shore Power Keeps Tripping the Breaker: Causes and Fixes

Every time I plug into shore power the pedestal breaker trips. What's causing it?

Modern marina pedestals have ground-fault protection of equipment (GFP) set around 30 mA, and it usually trips because current is leaking to ground somewhere on your boat, not because you're drawing too many amps. The leak is most often a wet or corroded shore-power inlet/cord, a failing water-heater element or battery charger, or wiring that lets neutral and ground touch on the boat. It can also be cumulative: several appliances each leaking a few milliamps that together cross the 30 mA threshold. Less often it's a true overload (too many loads on a small breaker) or a faulty pedestal. The key diagnostic split: if it trips the instant you plug in with everything off, it's a ground fault; if it trips only after you switch loads on, suspect a specific appliance or an overload.

ℹ️ Reference only: For general reference only: AI-assisted and not professional advice. This guide guarantees no result; every situation differs. Verify against the manufacturer, local codes, and a licensed professional before acting, especially for electrical, gas, fuel, plumbing, structural, or roof work. Use at your own risk.

💵 $0-$30 DIY to inspect and isolate; $100-$250 for a new marine shore-power cord (30A; 50A runs higher), $40-$120 for a water-heater element. A marine electrician runs roughly $120-$175/hr; a full ELCI/inlet/wiring diagnosis and repair typically $250-$700 at a shop. ⏱ 30-90 minutes to inspect and isolate the cause; 1-3 hours to replace a cord, inlet, element, or charger; longer if a wiring fault must be traced. ● Use caution

Safety: This is shore-power AC; it can kill. Always unplug at the pedestal before handling cord ends or working on the inlet, and treat circuits as live until verified dead with a meter. A ground fault on a boat is also an in-water electrocution (Electric Shock Drowning / ESD) hazard. Never let anyone swim near a boat or dock connected to shore power, and take the tripping seriously rather than bypassing it. Do not 'solve' nuisance trips by upsizing the breaker or defeating the GFP/ELCI; that removes the very protection guarding against shock and dock-wiring fires. If you smell burning or see melted/scorched connectors, stop and get it inspected.

Common causes

Moisture or corrosion in the shore-power cord ends or the boat's shore-power inlet, creating a path to ground (green/salt-crusted pins, burnt/melted connector, water intrusion). (most common)
Quick check:
A leaking appliance: most often the water-heater element or the battery charger, passing small current to the green safety ground, tripping a 30 mA ground-fault device long before a normal overload breaker would notice. (common)
Quick check:
Cumulative leakage: no single bad device, but several appliances each leaking a few milliamps to ground that sum past the ~30 mA threshold. Common on older boats with multiple AC loads; isolate by switching items off one at a time. (common)
Quick check:
A neutral-to-ground connection or fault on the boat (miswired outlet, generator/inverter transfer issue, or a previous owner's bonded neutral) that the ground-fault device reads as leakage. (common)
Quick check:
True overload: too many loads (AC, water heater, charger, heater) on a 15 A or 20 A pedestal circuit, tripping the thermal/magnetic side of the breaker. (less common)
Quick check:
Faulty or worn pedestal breaker/receptacle, or another boat on a shared circuit: verify by testing a different pedestal. (rare)
Quick check:

How to fix it

Note WHEN it trips. Trips the instant you plug in with the boat's main AC breaker OFF = ground fault (wiring/inlet). Trips only after you energize the panel or switch on a specific device = that device, cumulative leakage, or an overload. This split drives everything below.
Inspect the shore-power cord and inlet first. Unplug at both ends and look for green corrosion, heat discoloration, melted plastic, bent/loose pins, or moisture. Burnt or corroded connectors are the number-one cause. Replace any damaged cord or inlet with marine-rated, ABYC-compliant parts (correct 30A or 50A locking configuration); do not substitute hardware-store RV or extension cords.
Isolate by elimination. Turn OFF every AC branch breaker on the boat's panel, plug in, then switch loads on one at a time. The load that trips the pedestal is your leaker: commonly the water heater or battery charger. If it only trips with several loads on at once and each is fine alone, you're looking at cumulative leakage.
Test the prime suspects. A water-heater element that has corroded or wicked moisture leaks to ground; disconnect it and re-test. Same for a battery charger. Unplug its AC feed and re-test. Replace a leaking element or a failed charger with the correct marine-rated unit.
Check for neutral-ground faults. On a boat, AC neutral (white) and ground (green) must be bonded at only one point, the active source. On shore power that bond is ashore, so the boat must have NO neutral-ground connection of its own; an onboard generator or inverter has its own bond that the transfer switch makes active only when that source is running. A miswired receptacle or a transfer setup that leaves a second bond on the boat will trip the ground-fault device. This is ABYC E-11 territory. Verify with a meter or have a tech check it.
If nothing on the boat trips it, test a different pedestal or have the dock master check the pedestal breaker and GFP device. A worn pedestal device can nuisance-trip.
Fit a boat-side ELCI if you don't have one. ABYC E-11 requires a 30 mA Equipment Leakage Circuit Interrupter at the boat's main shore-power feed. It localizes the fault to your boat and is a real shock-prevention safeguard, especially against in-water electrocution (ESD) risk.
For actual overloads, shed loads (don't run water heater + AC + charger together on a 15 A pedestal) or move to a higher-amp pedestal. Never replace a tripping breaker with a larger one to 'fix' it, and never defeat the ground-fault protection. That removes the very safeguard against shock and dock-wiring fires.

DIY or call a pro?

DIY-friendly for inspection and isolation: checking the cord/inlet, eliminating appliances one at a time, and replacing a corroded cord or a failed water-heater element/charger are all within a competent owner's reach. Call a marine electrician (ABYC-certified) if the trip points to a neutral-ground bond, hidden wiring fault, generator/inverter transfer issue, or if you can't localize it, and for any ELCI install or panel rework. Live AC troubleshooting on a boat is unforgiving; if you're not comfortable working on energized circuits, hand it off.

Tools & parts

Marine-rated shore-power cord (ABYC-compliant, correct 30A or 50A locking configuration)
Marine shore-power inlet (stainless/marine-grade, sealed) if replacement needed
Digital multimeter (AC voltage + continuity/resistance)
Clamp meter able to read low milliamp leakage (clamp all current-carrying conductors together to read net ground leakage)
30 mA ELCI (Equipment Leakage Circuit Interrupter) for the boat's main, ABYC E-11 compliant
Replacement marine water-heater element or marine battery charger as needed
Dielectric grease / corrosion-block for connector pins
AC outlet tester and basic insulated hand tools

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Based on: ABYC (American Boat & Yacht Council) Standard E-11, AC and DC Electrical Systems on Boats; BoatUS / BoatUS Foundation (shore power and Electric Shock Drowning guidance); NFPA 303, Fire Protection Standard for Marinas and Boatyards (and NEC Article 555, Marinas and Boatyards); USCG / USCG Auxiliary boating safety guidance; NMMA (National Marine Manufacturers Association)

General marine-maintenance guidance, not a substitute for a qualified marine technician or surveyor. Boats and conditions vary; for fuel, electrical, fire, or structural issues (or anything safety-critical), consult a professional. Always follow your engine and equipment manuals. Information here is general reference only and may be estimated or AI-assisted. It is not professional advice. Verify with a qualified professional before acting, and use it at your own risk. See our Terms & Disclaimer.