I was inspired by the article at:
http://wmunderway.8m.com/cont/smoke/smoke.htm
I can't offer design specifics, but a few hints:
1. 12 or 6v works, either way you'll suck amps... but you do need to experiment with the length and gage of the nichrome heater wire... you want it glowing dull red in free air. Smaller gage needs less length to achieve this... but also has less hot surface area for smoke generation.
2. When the juice runs out in your reservoir, heat will build up quickly... enough to set a plastic tank on fire! (don't ask)
I want to design a thermal shutdown, but haven't yet. Best to use metal with insulation around, to save your boat.
3. Small computer fans are available for 5, 6, & 12v, check out www.jameco.com
Good luck!
Pat M