Answer:
Lead core trolling – as you probably know – is very speed dependent. The faster you go, the less affectively the lead core will sink. Also, moving into current lead core will not sink as fast. So here is a rule of thumb – at 2 mph one color of 18# lead (30 feet) will take a lure about 5 feet deeper. If you want to know precisely you will have to “sand test” your set up. Go to a gradual sand taper shoreline and start dragging your baits. Slowly go shallower and shallower until the bait starts ticking – record the depth for that setup. Repeat as needed.

Good Walleye Fishing