Shore Power, Propane and House Systems

Prerequisites

• You have sailed a cruising keelboat for a weekend or more, as in ASA 103 Coastal Cruising.
• You know what a seacock, a bilge and a battery switch are.
• You have read, or are reading, the charter check-out section of Bareboat Chartering (ASA 104).

Learning Objectives

This lesson covers the systems part of the ASA 104 Bareboat Cruising standard, for boats in US marinas and on US charters. By the end of it you will be able to:

• Connect and disconnect shore power in the safe order, and check polarity.
• Explain electric shock drowning, why you never swim in a marina, and what to do if someone is shocked in the water.
• Use a propane stove safely, with the solenoid, the tank valve and the gas alarm.
• Respond to a carbon monoxide alarm.
• Manage a house bank and a start battery so the engine always starts.
• Look after the fresh water system and the holding tank.
• Run through a daily engine check before the first start of the day.

Shore Power: 30 A and 50 A

In a US marina, the dock pedestal has one or more shore power outlets. On cruising boats you will meet two common sizes:

Your boat's inlet and cord must match the pedestal. Adapters exist, but use only a proper marine adapter from the charter company or marina, never a household extension lead or a home-made fix. Locking plugs twist to lock. If the locking ring or the cover is broken, do not use the cord.

Connecting (dead cord first, live last):

1. Turn off the boat's main AC breaker on the electrical panel.
2. Turn off the breaker at the dock pedestal.
3. Look over the cord. Do not use it if the jacket is cut, the pins are burned or discoloured, or it is wet.
4. Plug the cord into the boat first and lock it.
5. Then plug it into the pedestal and lock it.
6. Turn on the pedestal breaker.
7. Check the polarity light or alarm on the AC panel. If it shows reverse polarity, switch the pedestal off, unplug at the dock end and tell the marina.
8. Turn on the boat's main AC breaker, then the individual circuits you need.

Disconnecting is the same in reverse: boat main breaker off, pedestal breaker off, unplug at the dock end, then unplug at the boat and stow the cord.

The end you are holding is never live, so a dropped end cannot put current into the water.

Lay the cord so it cannot fall in the water or be pinched, with a little slack for the tide.

Electric Shock Drowning

Electric shock drowning (ESD) happens when electric current leaks into fresh or salt water from faulty wiring on a boat or on a dock. A swimmer in that water becomes part of the circuit. Even a small current through the body can paralyse the muscles, so the person cannot swim or shout clearly, and drowns. There may be no visible sign that the water is live.

The National Fire Protection Association and the US Coast Guard both give the same advice:

• Never swim in a marina, near a dock, or near a boat connected to shore power. This includes jumping in to clear a fouled propeller or retrieve a dropped hat.
• Keep children and dogs out of the water around docks.
• Have the boat's AC system checked by a qualified marine electrician regularly, and after any storm that affected the boat.

If someone in the water seems to be getting a shock:

1. Do not jump in. You will become a second victim.
2. Turn off the power: the shore power at the pedestal, and the dock's supply if you can reach it.
3. Throw a life ring or cushion and pull the person to the side. Use a non-conducting pole, such as a fibreglass boat hook, if you have one.
4. Call 911, or the Coast Guard on VHF channel 16. Tell the dockmaster.
5. Once the person is out, start CPR if they are not breathing.

Never assume the water is safe because the boat next door is new: older docks and boats often lack earth-leakage protection.

Propane and the Galley

Most charter boats cook on propane (LPG). It is efficient, but it is heavier than air. A leak does not drift away. It sinks into the bilge and lockers, where a spark from a pump, a switch or the engine can ignite it.

A typical installation has:

• A sealed propane locker on deck, with a drain at the bottom that leads overboard. Nothing else is stored there.
• A regulator and a manual valve on the tank.
• An electric solenoid valve, usually in the locker, switched from a panel in the galley. It closes when switched off or when power fails.
• A gas sniffer (propane alarm) mounted low near the stove, which beeps and often shuts the solenoid if it detects gas.

Lighting the stove:

1. Check the sniffer is on and not alarming.
2. Switch the solenoid on.
3. Hold a lit match or igniter at the burner, then open the burner knob. Many marine stoves have a flame-failure device, so you hold the knob in for a few seconds until it stays lit.

Shutting down: switch the solenoid off with a burner still lit, let the flame burn the gas out of the line, and then turn off the burner knob. Close the tank valve too when you leave the boat or go to bed.

If you smell gas or the alarm sounds: switch the solenoid off, turn off all burners, close the tank valve, put out any flame, do not operate switches or the engine, open hatches, and ventilate. Find the cause before you use the stove again.

Carbon Monoxide

Carbon monoxide (CO) is a colourless, odourless gas produced by engines, generators and stoves. The Coast Guard asks boaters to fit and maintain CO alarms inside the boat, and the boating industry advises a marine-rated alarm on any boat with a cabin and an engine, generator or gas appliance.

• Early CO poisoning feels like seasickness: headache, dizziness, nausea, tiredness. The Coast Guard advises treating seasickness symptoms as possible CO poisoning until you are sure.
• CO builds up when the engine idles or the generator runs, especially with the wind from astern or next to another boat's exhaust.
• Never sit on the swim platform or near the exhaust while the engine or generator runs.

If the CO alarm sounds: shut down the engine, generator and stove; get everyone into fresh air; open hatches and ports; and get medical help for anyone with symptoms. Do not silence the alarm and carry on. A "false" alarm usually means CO really was there.

Batteries: House and Start

Most cruising boats have at least two banks:

• A start battery, kept only for starting the engine.
• A house bank for lights, fridge, instruments, pumps and fans.

The battery switch may be labelled 1, 2, BOTH and OFF, or there may be separate switches for each bank and a parallel (emergency) switch. Ask at check-out which setting to use for starting, for sailing and at anchor. On many boats the normal setting is to leave the start bank alone and use the house bank, with the charging system feeding both.

The engine alternator charges the batteries while it runs. On shore power, a battery charger does the job. Some charter boats also have solar panels or a generator.

Conserving power on charter:

• Watch the battery monitor or voltmeter. Learn what "full" and "time to charge" look like on that boat.
• The fridge is usually the largest load. Keep the lid closed and do not overfill it with warm drinks.
• Run the engine to charge at sensible times, typically morning and evening when at anchor. Never in a crowded anchorage late at night.
• Never switch the battery switch to OFF while the engine is running. It can damage the alternator.

If the start battery is flat, most boats let you parallel the banks to start the engine. Do it as the charter company showed you, then return the switch to normal.

Fresh Water and the Holding Tank

Fresh water comes from one or more tanks through an electric pressure pump. Some boats also have a foot pump in the galley.

• Turn the pump off when you leave the boat, so a leak does not empty the tank and run the pump dry.
• If the pump runs on and off with no tap open, there is a leak somewhere. Find it.
• Showers, washing up under a running tap and rinsing gear empty tanks fast. A crew of six can use the whole tank in a day or two. Agree water rules at the start.
• Know where to fill each tank. Never put water in the fuel filler or diesel in the water filler.

The holding tank collects waste from the heads. The US rules on discharge, No Discharge Zones and securing the Y-valve are covered in US Boating Law & Pollution Rules. In practice:

• Before you sail, find the holding tank, its gauge if fitted, the deck pump-out fitting (marked WASTE) and any Y-valve or overboard seacock.
• Plan pump-out stops. Many marinas and fuel docks have a pump-out station, and some areas have pump-out boats.
• At the pump-out, open only the WASTE fitting. Seal the nozzle on the fitting, run the pump until the hose runs clear, then rinse.

The Daily Engine Check

Before the first start each day, run through a short check. A simple way to remember it is "FLOW BELT":

After starting, look over the side: cooling water should come out with the exhaust within a few seconds. If it does not, stop the engine and check the seacock and strainer. Then check the panel for oil pressure and charging, and listen for anything unusual.

For a full guide to diesel engines and fault-finding, see Engine Checks and Maintenance.

Worked Example: First Night in a Florida Marina

You pick up a 38 ft charter boat at 4 pm. The crew want to go swimming and then cook dinner aboard.

1. Swimming. You say no: the boat is in a marina with shore power all around. You walk to the beach instead.
2. Shore power. The pedestal has a 30 A outlet. You switch off the boat's main AC breaker and the pedestal breaker, plug in at the boat, then at the pedestal, switch on the pedestal and check the polarity light: normal. Then the main breaker on.
3. Dinner. You check the sniffer is on, switch on the solenoid and light the stove. After cooking you switch off the solenoid with a burner lit, let it go out, then turn off the knob.
4. Bedtime. You check the CO alarm is on, close the tank valve and turn off the water pump.
5. Morning. The FLOW BELT check finds the strainer half full of weed, so you clean it. You disconnect shore power in reverse order and start the engine: water comes out with the exhaust.

Common Mistakes

• Plugging in or unplugging with the pedestal breaker on, so the end in your hand is live.
• Jumping into marina water to clear a fouled propeller or retrieve something dropped.
• Leaving the propane solenoid on all day, or ignoring a beeping gas alarm.
• Running the house bank down overnight and then flattening the start battery too.
• Not watching for cooling water from the exhaust after starting.

Summary

• On shore power, dead end first: breakers off, plug in at the boat, then the pedestal, then breakers on and check polarity. Reverse it to disconnect.
• Electric shock drowning can kill with no warning. Never swim in a marina. If someone is shocked, cut the power and throw a flotation aid; do not go in.
• Propane sinks. Use the solenoid, burn the line dry, close the tank valve and never ignore the sniffer.
• Treat seasickness-like symptoms as possible CO poisoning. Fit and heed CO alarms.
• Keep the start battery for starting, save house power and water, and plan pump-outs.
• Check the engine every morning and look for exhaust water after starting.

Check Your Understanding

1. When connecting shore power, which end of the cord do you plug in first, and why? The boat end, with both breakers off, so the end you handle is never live and a dropped end cannot energise the water.
2. A child on the dock wants to jump in for a swim next to boats on shore power. What do you say? No. Leaking current can cause electric shock drowning, and there may be no sign the water is live.
3. You see a swimmer struggling by a dock, and you suspect electric shock. What do you do? Do not go in. Turn off the power at the pedestal or dock, throw a flotation aid, call 911 or channel 16, and start CPR once they are out if needed.
4. Why must the propane locker drain overboard from its lowest point? Propane is heavier than air, so leaking gas sinks and must be led out of the boat rather than into the bilge.
5. A crew member has a headache and nausea at anchor while the generator runs. What should you suspect, and what do you do? Carbon monoxide poisoning. Shut down the generator and engine, get everyone into fresh air, ventilate the boat and get medical help.

Sources

• https://www.nmma.org/certification/products/brochure/21402
• https://www.discoverboating.com/sites/default/files/2025-12/electrical_shock_hazards_brochure.pdf
• https://www.michigan.gov/dnr/things-to-do/boating/esd
• https://www.esfi.org/electric-shock-drowning-water-and-electricity-dont-mix/
• https://uscgboating.org/recreational-boaters/carbon-monoxide-protect.php
• https://www.discoverboating.com/sites/default/files/2025-12/carbone_monoxyde_detectors_brochure.pdf
• https://www.epa.gov/vessels-marinas-and-ports/no-discharge-zones-ndzs-state