In Your Engine Room

Do you routinely inspect the exhaust systems of all the propulsion and auxiliary engines abroad your boat?

Gasoline engine exhaust is the most common, but far from the only source of carbon monoxide.  Follow these four steps when inspecting every exhaust system: (1) Look and listen for leaks in the exhaust system, including a visual check at each joint for discoloration, water leaks, carbon, stains, etc.; (2) Check that all exhaust clamps are free of corrosion, in good repair, and are properly tightened; (3) Make sure all ventilation systems are in good repair and are not obstructed, restricted, or punctured; and (4) Make sure gaps around engine room and exhaust system doors, hatches, and access panels are minimized to reduce the opportunity for carbon monoxide to enter the cabin.

Can you inspect the full run of your exhaust system?

In many boats, especially double cabin vessels, the exhaust lines pass through the aft cabin on their way to the transom.   You must be able to inspect every joint and every flexible component for wear, cracking or loosened clamps.  If the exhaust lines run behind cabinetry, install inspection ports or removable panels in the cabinetry.

Other Sources Of Carbon Monoxide

Never install a portable electric generator below deck.  At the time of this writing, no portable generator meets Coast Guard Electrical and Fuel System Standards.  With the fuel tank above the generator directly above electrical components that are not ignition-protected, a potentially serious fire hazard exists.  Also, exhaust systems are rarely constructed of marine alloys and may rust through after brief exposure to a marine environment.  Do not use any flame-producing device in a non-ventilated area.  Alcohol heaters and stoves, propane heaters and stoves, catalytic heaters, oil or gasoline lamps, and charcoal stoves and grills consume oxygen.  As oxygen levels in an enclosed space fall, fuel is incompletely burned and carbon monoxide is produced.   A clue this is happening is that a normal blue flame becomes yellow and smoky.

In Your Engine

Are the main propulsion and auxiliary engines aboard your boat operating properly?

A properly engine is essential to eliminate carbon monoxide hazards.  Carbon monoxide is most often produced in the following areas:

Fuel system: Fuel that is contaminated, stale, or of the wrong octane number for the engine.
Carburetors/injectors: Dirty or clogged flame arrester, malfunctioning automatic choke or faulty adjustment of manual choke plate, worn flat needle valve and seat, high float level, incorrect idle mixture adjustment, and dirty or worn injectors.

Ignition System: Fouled or worn spark plugs, worn points or improperly gapped points, shorted or opened circuit high tension spark plug cables, and incorrect timing.

General Items: Worn piston rings and valves, low engine operating temperatures (cold-running engines increase carbon monoxide production, while engine operating at a higher end of the manufacturer's temperature range produce less), exhaust back-pressure caused by modifications to the exhaust system, and restricted engine compartment ventilation.

Operating Your Boat Safely

If all boat engines produce carbon monoxide, can I operate safely?

Yes, you can!  If you keep a steady flow of fresh air moving through your boat you will eliminate much if not all of the hazard.  The danger comes when there are pockets of stagnant air loaded with carbon monoxide that are not flushed from your boat.

Can I stop the "station wagon" effect and make my boat safer?

Backdrafting, or the "station wagon" effect occurs as air moves around a boat and forms a low pressure area immediately behind the broad, flat transom.  Carbon monoxide from the exhaust system entering this low pressure area is fed back into the cockpit and into cabin.  A similar low pressure area may be created behind a windshield or even the boat's cabin or wheelhouse.  If you open a foredeck hatch and let the fresh air flow through the boat this could be eliminated.  Opening a wind screen or vent in the fore part of the pilot house also will purge the stagnant air in the area of the cabin.

Are there other ways for carbon monoxide to get aboard my moving boat?

Unfortunately, yes.  If you alter the configuration of your boat, even doing something as minor as adding a canvas dodger around the cockpit, you change the potential airflow and the ability of the boat to purge itself of carbon monoxide.  While your guests might think it more comfortable to be out of the wind, a safe skipper realizes that an alternate source of air is a vital safely measure.  If you can feel a flow of air coming through the cockpit and cabin from an open forward hatch and/or port in the windscreen, you probably have little to be worried about.

If I shut down the engines on my boat, have I eliminated the risks?

Not if you are moored near another craft.   Carbon monoxide from an adjacent boat can invade your boat through hatches, doors, or even drains.  While you may believe that opening your boat to a flow of air is enough of a safety practice, reality is that the incoming air may bring a deadly cargo.

Do you minimize the time between engine start-up and getting underway?

Carbon monoxide production is greater while combustion chamber surfaces and gas passages are cool.  To minimize carbon monoxide production, skippers should ventilate their boats, orient their boats so that they will permit the maximum dissipation of carbon monoxide, and minimize the time spent getting underway.

Three overcome by carbon monoxide fumes while on fishing trip

Associated Press

CLEARWATER, Fla. - Three people on a fishing trip were overcome by carbon monoxide fumes as they napped below deck, and required medical attention when the boat returned to shore, officials said.

There were nine people on the 40-foot Wellcraft cabin cruiser when it left for an approximately five-hour fishing trip, said Joel Gray, the Clearwater fire marshal.

After the boat returned to the dock shortly after noon on Sunday, the three people - a young woman and two men - couldn't be awakened, Gray said.

Rescue crews determined they had suffered carbon monoxide poisoning. Though officials said the gas likely came from the boat's diesel motor, they were investigating how it entered the cabin.

The three victims, who were not identified, were first taken to Morton Plant Hospital, then transferred to another medical facility so they could be treated in a hyperbaric oxygen chamber, rescue officials said.

The victims' conditions and the name and location of the second medical facility were not given.

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