Contrary to what most people believe, trolling has to be very exact if you are going to be effective. Where you troll is only a small part of the total presentation. Water temperature, water depth, lure depth, lure color, lure size, lure action, speed of presentation, direction of presentation, wind speed, wind direction and surrounding structure all play important parts in how effective trolling will be for you. Temperature is a key factor involved in locating walleyes. It controls the depth fish are in and where oxygen and food are.
Depth is very important when trolling for large fish.
Large basins with areas of uniform depths are vital. Most trolling for walleyes is done in 20 to 40 feet of water. Lure action and color has to match the forage at the time. The most effective lure you have will be the color and have the right action to trigger a strike. Depths may have to be changed several times a day, your lure has to be kept in the strike zone.