A fter many years of declining, the number of cases of carbon monoxide poisoning cases is on the rise. In the last 30 years, huge strides have been make toward making marine engine exhaust systems safe, particularly the gasoline engine which puts out more than double the amount of CO that diesel does.
Carbon monoxide is an odorless gas that is a combustion by-product of both gas and diesel engines.
When inhaled by the human body it is most dangerous because it interferes with the blood system and most especially the brain. In smaller doses it results in temporary illness if you are lucky, and brain damage if you are not. In larger does it causes internal hemorrhaging and death. Sleepiness and headaches are the primary symptoms. While CO itself is odorless, one can always be sure that it is present by the distinct smell of the engine exhaust.