CO and Propane Alarm Installation Guide for Boats

Why CO and Propane Alarms Are Non-Negotiable

Carbon monoxide (CO) is the leading cause of boating fatalities that don't involve drowning. It's colorless, odorless, and can incapacitate a person within minutes at high concentrations. Propane and other LPG gases are heavier than air — they sink into bilges and low spaces where a single spark can cause an explosion.

Neither threat gives you a warning you can see or smell. A properly installed alarm is the only reliable protection for your crew.

This guide covers what you need to know to install CO and propane/LPG detectors correctly on your boat, following ABYC (American Boat and Yacht Council) standards.

Understanding the Two Threats

Carbon Monoxide (CO)

CO is produced by any combustion engine or appliance: your main engine, generator, gasoline-powered appliances, and even neighboring boats at a marina or raft-up. It accumulates in enclosed spaces — cabins, cockpits with canvas enclosures, and swim platforms near the transom exhaust.

ABYC standard A-24 governs CO detector installation on recreational boats.

Propane / LPG

Propane is used for cooking on many cruising and liveaboard boats. Because it's heavier than air, any leak flows downward and pools in the bilge — creating an invisible explosion hazard. ABYC standard A-1 covers LPG systems on boats.

Note: CO detectors and propane/LPG detectors are different devices. CO detectors sense carbon monoxide gas. Propane detectors sense combustible hydrocarbon gases. Some combination units detect both — confirm what your unit detects before purchasing.

What You'll Need

CO detector (ABYC A-24 compliant, UL 2034 listed) and/or propane/LPG detector (UL 1484 listed)
Wire strippers and crimping tool
Marine-grade tinned wire (appropriate gauge for your run length)
Inline fuse holder and fuse (typically 1–3A)
Marine-grade ring and butt connectors
Heat shrink tubing
Drill and bits
Cable ties and adhesive mounts

Browse our Marine Safety collection for CO and propane detectors, and our Electrical collection for wiring supplies.

Step 1: Choose the Right Detector

CO Detectors

Look for units specifically rated for marine use. Automotive and residential CO detectors are not suitable — they aren't designed for the vibration, humidity, and temperature swings of a marine environment. Confirm the unit is:

Listed to UL 2034 or equivalent
Rated for 12V DC operation (most marine units)
Designed for the vibration and moisture levels of a boat

Propane / LPG Detectors

Marine propane detectors typically include a solenoid valve connection that automatically shuts off the propane supply at the tank when gas is detected. This is the preferred setup — detection alone without automatic shutoff leaves a manual response step that may not happen fast enough.

Combination Units

Some units detect both CO and combustible gases. Verify the unit's listing covers both threats before relying on it for both functions.

Step 2: Determine Placement — CO Detector

CO detector placement follows ABYC A-24. Key rules:

Install in every enclosed space where people sleep or spend time: cabins, berths, saloons
Mount at head height (approximately 4–5 feet above the sole/floor) — CO is slightly lighter than air and distributes throughout the space
Do not mount within 12 inches of cooking appliances, air supply vents, or areas subject to direct spray
Do not mount in the engine room — CO levels there will always be elevated during operation; the alarm is meant to warn of CO reaching living spaces
For boats with a cockpit enclosure, consider a detector in the cockpit as well

Swim platform / transom area: CO from the exhaust can accumulate at the stern, especially at idle or when the boat is stationary. Keep crew off the swim platform when the engine or generator is running.

Step 3: Determine Placement — Propane Detector

Propane is heavier than air, so placement rules are the opposite of CO:

Mount as low as possible in the space — within 12 inches of the sole (floor) where propane will accumulate
Install in the galley or any space where propane appliances are used
Install in the bilge or lowest accessible space if propane is stored or routed through the boat
Do not mount near the propane appliance itself — normal cooking vapors can cause nuisance alarms

Step 4: Wire the Detector

Most marine CO and propane detectors wire directly to the boat's 12V DC system. They should be powered continuously — not switched — so they protect the boat even when the main panel is off.

Run marine-grade tinned wire from the detector location to your fuse block or battery bus
Use an appropriately sized fuse (check the detector's manual — typically 1–3A)
Connect the positive wire to a non-switched fused circuit
Connect the negative wire to the common negative bus
Secure all wiring with cable ties every 12–18 inches; protect runs through bulkheads with grommets

Browse our Electrical - Fuse Blocks & Fuses collection if you need to add a dedicated circuit for your detectors.

Step 5: Wire the Propane Solenoid Valve (If Equipped)

If your propane detector includes a solenoid valve output, the valve installs at the propane tank and wires back to the detector:

Mount the solenoid valve at the propane locker, on the tank outlet
Run two-conductor wire from the solenoid back to the detector's solenoid output terminals
The detector controls power to the solenoid — when gas is detected, it cuts power to the solenoid, closing the valve and shutting off propane flow
The solenoid should also be wired to a manual on/off switch at the galley so the cook can shut off propane without going to the tank locker

Step 6: Mount the Detector

Use the provided mounting template or bracket to mark screw hole locations
Drill pilot holes (use a backing plate on thin fiberglass panels to prevent cracking)
Apply a small amount of marine sealant around any holes that penetrate a watertight surface
Secure the detector with stainless steel screws
Connect the wiring harness and snap the detector into its mounting bracket

Step 7: Test the System

After installation, test the detector before relying on it:

Power-on self-test: Most units run a self-test on startup — confirm the alarm sounds and the indicator light functions
CO test: Use a CO test gas aerosol (available from marine safety suppliers) to verify the sensor responds and the alarm activates
Propane test: Briefly expose the sensor to a small amount of propane (from a lighter, held several inches away) to verify detection and solenoid shutoff
Solenoid test: Confirm the solenoid valve closes when the alarm triggers and reopens when reset

Test your detectors at the start of each season and replace them per the manufacturer's recommended service life (typically 5–7 years for CO detectors).

Maintenance and Replacement

CO detector sensors have a finite lifespan — most are rated for 5–7 years. Replace the entire unit, not just the sensor, at end of life
Keep detector faces clean and unobstructed — do not paint over them or cover with tape
Test monthly using the test button; test with test gas annually
Log your installation date so you know when replacement is due

Pro Tips

Generator exhaust: Generators are a major CO source. If you run a generator, install a CO detector in every enclosed space and consider an exterior-mounted detector near the generator exhaust outlet
Neighboring boats: At a marina or raft-up, CO from another boat's exhaust can enter your cabin. Keep hatches and ports closed when neighboring boats are running engines
Never ignore an alarm: If your CO alarm sounds, immediately move everyone to fresh air, start the engine blower, open all hatches, and do not re-enter until the source is identified and resolved
Propane locker ventilation: Ensure your propane locker is properly ventilated overboard — any leaked gas must be able to escape the boat, not accumulate in the locker

Shop Marine Safety at Egret Marine

Browse our full Marine Safety collection for CO detectors, propane alarms, fire extinguishers, and other essential safety equipment. Don't wait until next season — safety gear is one upgrade that should never be deferred.

Questions about marine safety equipment? Contact the Egret Marine team — we're here to help you keep your crew safe on the water.