I just got an 8gal kettle and used it today for my first full volume boil. I made and APA. I put about 6 gallons into it and put it on the burner. I have a big burner on my stove. I has two concentric rings of flames. I could easily boil 4 gallons in my old kettle, but my new one never reached a hard boil. It did boil though. I've heard before that there needs to be a hard boil to get proper hop utilization. Is that true? Should I be worried?