I can cover a lot of empty water, and I never stop my boat until I know I am over fish. There is a lot more to trolling than just going for a boat ride. I will fish with as many rods allowed, up to three anglers, and I will fish each rod with a different pattern, until I know what the salmon prefer. The most critical factor in trolling is speed. You will here a lot of argument about how fast.
Tidal movement determines trolling speed.
How fast you troll will change radically depending on whether you are running with the tide or against it. I fish flyrods with a floating line, a nine foot leader, and the trolled flies I described earlier. A bulky store bought fly, on a spinning outfit is going to swim differently and thus would have to be fished at a different speed. I generally fish all the flys at the same distance from to the boat. A rule of thumb for me, is placing the flies just in back of the motor's bubble train.