This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
I have a cookbook here that says 165-170F. There is a lot of paranoia
about poultry being underdone. I haven't done any turkey yet (I have the
same smoker you do), but I've done several chickens and have had no
trouble pulling them off at 165F.
> The problem I am having is that although I follow the recipes exactly I
> have a very difficult time reaching this temperature. I installed an
> oven thermometer in place of the "cold - ideal - hot" thermometer that
> came with the smoker. I even placed a second thermometer inside to
The stock thermometer is worthless... I replaced mine.
Are you brining the bird before cooking? If not, I strongly recommend
you do. I took a class in grilling and barbequeing and for chicken parts
they suggested a brine of 1 cup kosher salt and 1 cup sugar dissolved in
1 quart of water. Soak the pieces for up to 90 minutes. Don't go longer
than this or the chicken will take up too much salt. I think the basic
idea here would work for turkey breast also, though I'd reduce the salt
to maybe 1/2 cup and soak the turkey for 3 or 4 hours. (For a whole
chicken they recommended 1 cup kosher salt in a gallon of water, brining
the chicken for 6 to 8 hours. I'd guess the turkey breast would be
somewhere in between the two methods.)
Also, you're going to have a tough time getting a turkey breast to 180F
if the external temp (external to the turkey) is only 20 or 30 degrees
warmer. To achieve an internal temp of 180F I'd push the smoker temp to
at least 240F. But, as I mentioned above, 180F is higher than you really
need to go. If the meat thermometer reads 165F and the juices run clear
when you pull the thermometer out, that bird is done.