A generator often runs for hours with the boat at anchor and people asleep or swimming off the stern. Its exhaust carries carbon monoxide, and the gas collects where the boat's shape traps it. That's why the generator gets its own look in a survey, apart from the main engines.
Why it matters
NIOSH has identified over 800 boating-related carbon monoxide poisonings, over 140 of them fatal. More than 200 were on houseboats and attributed to generator exhaust alone.
The CDC's investigation at Lake Powell found why. Houseboat generators exhausted into the air space beneath the stern deck, near the water. With the generators running, readings there ranged from 6,000 to 30,000 parts per million, and near the swim platform reached 7,200. The report calls those levels lethal within seconds to minutes. People who swam under the deck or sat on the platform died. The report also found that in 8 of 36 non-fatal poisonings inside cabins, the CO detector had been disabled.
How a surveyor checks it
Where the exhaust comes out. Find the outlet. An outlet under a swim platform, into a space under the stern, or close to a hatch, port or cockpit opening puts gas where people are. Note it whatever the condition of the parts.
The exhaust run. Follow it from the generator: the mixing elbow, hoses, muffler and water lift, and the outlet fitting. Look for scale and weeping at the elbow, soft or cracked hose, single clamps, and soot on surfaces near joints. See exhaust hose and exhaust elbow corrosion.
Running. Start the generator and check for leaks at every joint, water flow at the outlet, and fumes in the engine space and accommodation.
CO alarms. Check they're fitted where people sleep, in date and working. NIOSH advises testing daily. See no CO alarm.
What decides the grade
Where the gas can go. A leak inside the boat or an outlet under a swim platform is an A, and so is a generator aboard with no working CO alarm. Corroded or perished parts that aren't leaking yet are a B. Single clamps on a sound system are a C.