If you have an older one that doesn't spit and bubble even on low, I'd cook it it on low 8-10 hours hours or high 4-6 hours. If you have a newer model, like mine, that boils (not just simmers!) even on low, allow about 5 hours on low and don't even think about cooking it on high. Really, you just need to get to know your own slow cooker and follow their guidelines. There is a huge difference between newer and older models.