Do you remember a TV program called “Hill Street Blues”? It always started with the watch commander telling the new shift, as they were departing on duty, “Be careful out there.” We know to put our life jacket on, to look for other boats, to post a spotter for watersports, to file a float plan, etc. But there’s one more safety item to think about, especially as cruisers, which are getting smaller, and center consoles, which are getting bigger, increasingly use outboards for power.
A little background that we may have forgotten. Engine combustion emissions are a combination of CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxide). “Greenhouse gases” that eat up the atmosphere and contribute to the Earth’s warming are mostly a product of HC and NOx, both of which are present in large amounts in two-stroke outboards, regardless of the type of fuel induction (not counting direct injection, which I’ll get to in a moment).
The easiest way to reduce HC and NOx is to use available technology and produce four-stroke outboards. Voila! The industry has met the EPA mandate of reducing damaging emissions. But, if two items are modified, the other one, by scientific law, is also modified. Reduce HC and NOx, and CO increases. Which isn’t bad, unless staying alive is one of your life’s priorities.
If you remember “Hill Street Blues,” I’ll bet you remember something called “the station wagon effect.” Older (pre-1990s) station wagons had flip-up rear windows above the tailgate door. Having that window up allowed cool air to be drawn into the car — along with the silent killer, carbon monoxide. You’d think such a dramatic lesson would be remembered, but did anybody give you a warning when you got four-strokes installed on your big center console — have you seen some of those things lately? — or when you got the winter enclosure made for your T-top?
Now, here’s where boats differ from cars: With a car, more CO is drawn into the car the faster it goes. The faster the boat goes, however, the more the CO is mixed with clean air, offsetting most of its dangerous effects.
With the boat, the EPA measures the CO at dead (sorry) idle. Non-catalyzed
I/Os have the worst CO readings, accounting for most emission-related deaths, followed by outboards: four-stroke carbureted and then four-stroke EFI. The two-stroke direct-injection engine, by virtue of its fuel delivery management, registers nearly zero emissions. Especially CO.
At what speed do you troll for the elusive rockfish? According to the computer downloads I see, between 700 and 1000 rpm. All. Day. Long. That’s the perfect speed to draw the odorless CO into the new enclosure you just had made for your boat. Unless you troll at 20 mph, you need to be especially cautious. Make sure you open another curtain for ventilation, and non-retention of carbon monoxide.