Temp control doesn't work for boiling, as boiling occurs at 212F/100C, regardless of how much energy you're dumping into the pot.
I.E., I have a boiler that will maintain a boil (at 212) at 45% power of the element. It will also maintain a boil (also at 212) at 100% power. Boiling at 212 is a constant (altitude/pressure arguments aside). You can control how vigorous the boil is, but not the temperature of the boil.