Our Saginaw bay rule of thumb w/boards, in-line or tethered.
Usually pull spinners 1.5 - 1.8 mph (GPS ground speed) Usually slower in cooler water a little faster in warmer waters. Use your turns as an indicator if the fish are hitting the inside lines it tells ya they want it slower if hitting the outside lines then speed up a little. Once the fish start showing a preference for lures trolled in the 2.0+ mph range we start switching to spoon harnesses, Hot n Tots (cranks), and Spoons , lures that are more tolerant to those speeds.
Inland waters my favorite is a Roach Rig or Lindy floater rig slowly back-trolled along weed edges