By Don Leutz, Northern California/Lake Tahoe Chapter
Carbon Monoxide Poisoning is sometimes called the “Silent Killer,” since Carbon Monoxide (CO) is a colorless, odorless and tasteless gas. You simply do not know it’s there, but it can be quite deadly, especially while boating. Both prolonged exposure to low concentrations of Carbon Monoxide or short periods of exposure to high concentrations of Carbon Monoxide can kill you.
There can be multiple sources of Carbon Monoxide on a boat, depending upon the type and size of boat and the various engines and appliances that might be on board. The primary source of Carbon Monoxide on our Classic Boats is the engine. However, some boats are larger which have gasoline generators, gas cooking ranges, space and water heaters…all of which can cause Carbon Monoxide poisoning to the unsuspecting. Carbon Monoxide is a by-product of the combustion of any carbon based fuel such as gasoline, propane, charcoal and wood.
CO can accumulate anywhere in or around your boat, including the rear deck, swim platform, or in the water around the exhaust pipes. Exhaust leaks, which are the primary cause of carbon monoxide fatalities, can allow CO to migrate throughout the boat and into enclosed areas. Be sure to check all exhaust hoses, hose clamps, and fittings for leaks or cracked or charred sections and repair or replace as necessary. Confirm that cooling water flows from the exhaust outlet when engines are started. It is also a good idea to inspect the cylinder head, exhaust manifold and water injection elbow for cracks or leaks.
Carbon Monoxide can remain in or around your boat at dangerous levels, even if your boat engine is shut off. Boats around you might also be causing CO to develop unsuspectingly. The so-called “station wagon effect” is something to be aware of while boating. This “station wagon effect” causes a kind of back draft from the exhaust that pulls the exhaust fumes and gases back into the boat from the rear while the boat is moving forward. This effect can be caused by wind or it may be caused by the boat movement itself. Or, exhaust can re-enter a boat if it is moored too close to a dock or another boat, or it can be pushed back into a boat by the prevailing winds. If you can smell engine exhaust, you are inhaling Carbon Monxide. However, even if you cannot smell the exhaust, you still may be inhaling CO and not even know it.
Symptoms of Carbon Monoxide poisoning include, irritated eyes, headache, nausea, weakness, and dizziness. These symptoms are often confused with seasickness or intoxication, so those affected may not even know that they have been poisoned by CO or they might not think much about it, before it’s too late.
Thankfully, there are some things that can be done to greatly reduce the effects of Carbon Monoxide poisoning:
1. Maintain fresh air circulation throughout the vessel always, especially on boats with enclosed spaces.
2. Know the location of your engine exhaust outlets and keep everyone away from these areas.
3. Stay off the aft deck and swim platform while the engine(s) is running. If swimming, be sure the engine is off and that you maintain a distance from the engine exhaust. Do not enter any areas under the swim platform where exhaust outlets are located.
4. Take immediate action to ventilate the boat, if exhaust fumes are detected.
5. Keep forward facing hatches and vents open to allow fresh air to circulate throughout the vessel, even in inclement weather.
6. Install a marine grade Carbon Monoxide Detector on the boat, particularly if there are any enclosed spaces. The Detector will sound an alarm should it detect harmful CO fumes. If an alarm takes place, ventilate the boat immediately.
7. Change course and speed to head into the wind to improve ventilation.
8. Keep your engine tuned up to manufacturer’s specifications. Engines in tune produce less CO.
Should a passenger or crew member experience any of the symptoms of Carbon Monoxide poisoning, get the individual into the fresh uncontaminated air as soon as possible and, if necessary, seek medical treatment. For more information on Carbon Monoxide poisoning, visit: www.uscgboating.org.
Originally printed in the Fall 2026 issue of the Northern California/Lake Tahoe Chapter newsletter, Western Wood.