I've smoked a bunch of birds in my Brinkman electric over the years - it's great stuff.

I've found that most meats including turkey will need to cook an hour per pound. Make sure to keep hot water in the pan to within 1/2" of the top. Don't open the lid too much or it'll never get done. I use "smoke on" for the first hour or two, then let the bird go for a few more hours with no chips for smoke, then keep chips in the rest of the time (unless I'm sleeping - an 18 pound bird takes 18 hours to smoke!). Don't over cook. It'll dry out.