Oh just wait... once you think you have the speed nailed, the wind changes, the currents change, the weather changes and you are back on the water tomorrow starting from stage one!!! Some days they want it at 1.3 other days it is 1.8.

Might blow your mind on this one, but current plays a big part in how fast the bait is traveling. I have a pretty decent explaination about it in the walleye section on the Michigan forum.