I'm not a big trolling guy but I can tell you varying your speed will increase your catch rate. A slow reaction strike or a fast aggressive strike all depends on the fishes mood, and you have to cater to that.
Why 60 fow? Is that the depth you usually fish at? Does 60' have any significance? PM me and I'll give you a good starting point for Macks at Granby.so trolling with the 20hp jonson would not be to fast for lakers in say 60fow?