The neoprene hose came from the auto parts store. The plastic through the transom fitting came from West (Its Mar... something), and the right angle barbed plastic hose fitting came from ACE.

I too was concerned about the heat before I did this. However, none of the components gets hot or even significantly warmer than the engine cover. Heat is not a problem. The only two problems I can envision are corrosion (the gasses are corrosive, I assume), electrolysis (that is why I used plastic), and a buildup of unburnt oil in the exhaust tube and fittings (I'll find out about this one when the boat is pulled for the season.)

Incidentally, I have probably burnt almost 100 gallons of gas this summer, so it has had a suitable trial period.