JEM Watercraft

Would your PFD keep your mouth and nose above water if you were unconscious or incapacitated? Is this too much too expect of a PFD?

I don't think mine (a vest) would do so, (I will try it out by getting in the water and pretending to be knocked out), I doubt mine would keep my breathing holes out of water because it has no more flotation around the upper chest than it does around the upper back;
Maybe the weight of my legs would keep my body somewhat upright in the water, but probably not so perfectly as to prevent my face going into and out of the water repeatedly. The face would only have to be in the water a fraction of a second at a time to suck in enough water to initiate drowning I would guess.

I guess the question brings to bear the principal of practicing ahead of time all our worst –case scenarios where possible.

Depends on which type you have. Generally speaking if it has a big thick collar that goes behind the head it should keep you in a safe position in case of loss of consciousness. In Australia the various types can be seen here:
http://www.transport.wa.gov.au/imarine/ ... p#standard
Other countries might have different descriptions but this kinda covers it. As for practising unconsciousness that might prove painful
Cheers John.

Type 1 pfd is the most likely to keep your head out of the water. OK on a boat but I wouldn't like to paddle in one. Maybe a self inflating vest but if you get wet, you'll end up looking like the michelin man . If you are kayaking close to ocean washes or in any fast moving water, maybe a helmet is the go. If it's boat traffic that is the concern, a flag mounted with a light aids visibility. Apart from that, it's safest to always go kayaking/canoeing with a mate.
All the best.