You guys, ( well, a few of you anyway ), seem to be concerned with "not enough air' getting to the engine with the cover down, and just now, about opening the cover to vent "gasses". I could be mistake here, but, isn't it a regulation that the manufacturer equip boats with engine covers, with ventilation, usually a scoop facing forward on one gunwale and one facing backwards on another gunwale? Isn't it some sort of regulation that boats built with covered engine compartments be equipped with a bilge "blower", that you run for a minute prior to starting the engine to clear any unwanted gasses from the bilge?( the "blower" switch on the instrument panel). If so, discussion of "no air", or "bad gasses", is likely moot I'd think.