Being a data nerd, I thought for sure I could quickly find comprehensive statistics to help quantify the relative risk. But no luck. I did find information the USCG site, including older data, but most of the material focused on educating re: the dangers of CO and avoidance. I found an article in boating mag documenting gas engines as producing 10x CO on equivalent horsepower (
https://www.boatingmag.com/how-to/fatal-fumes/). I tried to find any reports on CO poisoning or death from a diesel-powered boat while underway but no luck there either. (I got one hit, but it turns out to be a truck driver (
https://pubmed.ncbi.nlm.nih.gov/186...t,and under suitable environmental conditions.).
The absence of evidence is not evidence of absence - I'm not suggesting CO isn't a real issue. I welcome anyone who is better at ferreting out government data. I'm just surprised, given the level of education and prevention (e.g., CO detectors required), that I couldn't quickly find annual statistics at least from the incidents where the USCG is involved. Maybe there are and someone else will point me to them!