Carbon Monoxide

Carbon Monoxide

Carbon monoxide (CO) is a deadly gas that enters the body through the lungs and cuts off the oxygen, causing death in minutes. It is colorless, odorless and tasteless and is toxic in even very small quantities. Symptoms of CO poisoning are similar to those of the flu– headaches, fatigue and nausea. Carbon monoxide may come from the boat’s engine or any cooking or heating appliances that run on gas or propane.

Each year, many people who operate or are around boats die from the effects of carbon monoxide. Nearly all of such deaths or injuries are preventable. As a boat operator it is important to be aware of carbon monoxide poisoning prevention practices.

Smoke being thrown from a larger to a smaller boat

To avoid poisoning, boaters should idle the boat’s engine only in well- ventilated areas so that the tail winds cannot carry CO back on board the vessel. All fuel-burning engines or appliances should be approved for marine use to be used on board a watercraft.

Other safe practices that help to prevent CO poisoning include:

  • Having the boat regularly inspected and serviced by a professional
  • Trusting the marine-rated CO detector and reacting appropriately when the alarm sounds
  • Heating and cooking only in well-ventilated areas

CO can collect within a boat in many different ways.

Exhaust Leaks

Exhaust leaks are the leading cause of carbon monoxide fatalities in boating. When an exhaust leak occurs, carbon monoxide is allowed to travel throughout the boat and into enclosed areas. Exhaust leaks can occur from various CO sources, including engines, propane appliances, generators and grills.

Even if the exhaust is properly vented, some special circumstances can allow the exhaust to re-enter the watercraft. Those circumstances include when two vessels are tied together or moored closely together, when the boat is docked alongside a seawall, when a fuel-burning appliance or engine is running while the vessel is idle and when the load on the boat causes the bow to run high.

Boats are also at risk for exhaust leaks when cruising under certain conditions, especially with canvas in place, which produces the “station wagon” effect. Enclosed spaces near the stern swim platform can also allow exhaust to collect. Therefore, it is especially dangerous to swim near the stern of the watercraft when engines or other carbon monoxide-producing devices are in operation.

To help prevent carbon monoxide poisoning risks from exhaust leaks, boat operators should:

  • Ensure that forward-facing hatches are open continuously to allow fresh air to migrate throughout enclosed spaces, even when the weather outside is not ideal.
  • Keep passengers clear of the rear deck area and the swim platform when engines or a generator is running, and always keep a close eye on the swimming area.
  • Avoid running engines or equipment for long periods of time while the boat is near a seawall, at a pier or close to another boat.
  • Have regular exhaust system and engine maintenance inspections performed by experienced professional mechanics.

 “Teak” Surfing

“Teak” Surfing is a hazardous activity in which participants hold onto the swim platform of a boat as it travels slowly through the water, surfing its wake. In many states, “teak” surfing is prohibited by law. This practice is extremely dangerous for a few different reasons. First, it places passengers very near to the boat’s propeller. Second, participants are exposed to dangerously high levels of carbon monoxide that are produced by the watercraft’s exhaust. The surfers can lose consciousness in just a few seconds.

Swimmer Teak Surfing behind a boat releasing smoke

Responsible boaters will not allow “teak” surfing from their vessel at any time. Other names for the dangerous and irresponsible water sport include “drag” or “platform” surfing.

Carbon Monoxide Checklist and Annual Maintenance

Proper operation and regular maintenance of the vessel are a boater’s best defense against carbon monoxide poisoning risks. In addition, the following is a checklist of preventative measures that should be completed before each trip onto the water:

Table 1.        Carbon Monoxide Checklist

Preventative Action


Test the performance of each carbon monoxide detecting device onboard.

Ensure that all exhaust clamps are in their proper place and are secured.

Look for any leaking exhaust from system components, which can be detected by corroded fittings, water leaks, rust or black streaking.

Inspected rubber exhaust hoses for sections that are burned or cracked and ensure that each hose is free of kinks.


Listen for changes in the exhaust sound, as they can indicate that a component is failing.


Make sure that cooling water runs from the exhaust outlet when the generator and engines are cranked up.



If any problems are identified during the pre-trip inspection, do not operate the vessel. Have a professional mechanic further investigate the findings before operating the boat.

In addition to the above preventative pre-trip checklist, all watercraft should undergo an annual maintenance inspection performed by a Qualified Marine Technician. At a minimum, the inspection and maintenance should include:

·        Inspection of each water pump impeller and the condition of the water pump housing. If there is any wearing or cracks, the housing should be replaced. Further information is available in the engine and generator manuals.

·        Replacement of any exhaust hoses that show evidence of charring, cracking or any other form of deterioration.

·        Full cleaning, inspection and confirmation of proper operation of the generator cooling water anti-siphon valve.

Examination of all metallic exhaust components for rusting, looseness, leaking or cracking. Close attention should be given to the water injection elbow, the cylinder head and the exhaust manifold.

Proper Response to Suspected Carbon Monoxide Poisoning

Signs of carbon monoxide poisoning

If a boater or passenger is showing signs of carbon monoxide exposure, including headaches, irritated eyes, dizziness, weakness or nausea, take the symptoms seriously and take action immediately. Do not mistake carbon monoxide poisoning for intoxication or seasickness, though the symptoms can be very similar.

In cases where poisoning symptoms are present, move the person immediately to fresh air, investigate the cause and take action to correct the problem. In most cases, medical attention should also be immediately sought.

The U.S. Coast Guard Boating Safety Division website provides additional information for boat operators about how to prevent carbon monoxide poisoning on recreational boats and can be accessed at