I don't have a speedo on my boat that works. So I use the angle of the dangle on the downrigger cable. Since I have two different weight sizes on the riggers I can get a pretty good indication of the speed needed. Basically I try to find the speed my gear starts working and then lower the ball. I then look at the angle the cable is at and keep it that way. When you make the turn to turn against the current you will need to slow down and vise versa.