Sometimes it's like driving a station wagon with the rear window open.
Sometimes it's a wind from aft that slightly exceeds your own speed, whereas a higher wind speed would blow it all away and you'd never smell it.
I agree... the station wagon effect.
most times, there will be a bit of a vacuum created in the cockpit of a boat as the wind comes over the bow and moves rearward.. so usually, air will come over the transom (where air movement is the least) and move into the low pressure area of the cockpit.... and to some extent, boat speed will play a role here as well.
this isnt specific to any certain type or model of boat, but is common to MOST of them, but
NOT ALL of them.
the difference could be in how the exhaust is dealt with, and how rich the engine runs... but in all cases it is an annoyance, and some cases, very harmful.... CO poisoning can creep up on you without any warning whatsoever.
its rare instances that CO poisoning happens to people in the open cockpit (it does happen), but its not so rare that it happens to people who are in the cuddy/cabin on long passages, where the CO can build up to very high levels....
..and remember that just because you dont smell any exhaust or other odors, does NOT mean that CO is not present.... a CO detector is a good thing to have onboard any boat that has an enclose space where fossil fuels are being used.
so just be aware...