I have been trying to figure out the best way to measure my trolling speed. I do not have a speedometer on my boat. I do have a fish finder with one of those wheels that spins below the boat and tells me speed and temp. I am not sure just how accurate it is . I have a tach on my kicker and that is usually how I control my speed. The problem is you could be either trolling with or against the tide. Using the tach will not keep you going the same speed both ways. I am curios as to how you guys and gals keep an consistant trolling speed. I basically use the feel from fishing for many years and get it dialed in so I am catching fish. I do think I could possibly increase my catch If I could control it better.