I spent several years trolling at 1-1.5 mph with sorry results! After some time I noticed that when we would take a fish (walleye) it was 2mph or more. My fishing partner was whining to slow down we would catch more fish. It is what I have always heard too. But now I do about 2mph or more and often catch my limit or close to it nearly every time I went out. That was two years ago the best fishing season I ever had! (Caught 98 Lake Erie) Didn’t get out much last year and when I did the weather was not in my favor.