My trolling speed is usually determined by the lure and its action. I have a Fish Hawk which tells speed and temp. at the downrigger ball and my average speed is 1.5 to 2.0mph. I have trolled at 2.5mph but not much faster than this. This is for Salmon and Browns. Usually when I'm on the lake the boats next to me are going faster, maybe they have streamer's??
Now for lake trout...... I go Slooooooow.