If you are keeping the water under a boil, you might think about trying a sous vide circulator. We’ve been using them here on quite a few different products and having a lot of fun and good results with them. Temperature control is extremely precise, and you don’t have to worry about cold spots since it automatically circulates the water.
We have been using the VacMaster SV1 and it works great! A couple less expensive models will be coming out very soon too from Weston. The SV1 will work with up to a 30 liter container of water, if that is comparable in size to what you are using in a turkey fryer.
We also just might be giving away a couple of the VacMaster SV1 Circulators in May… Keep an eye on our YouTube channel the first of next week…