Downriggers & Planer Boards

We have been fishing Lake Erie from my Brother-in-Law's boat, mainly for Walleye, using Downriggers & Planer Boards. We run a couple of Fish-Finders, so we know they are running heavy near the bottom, at about 65 feet. Trouble is that we are not sure we are getting down to the right depth.

We generally run at 2.0 MPH, but one day I wasn't along I heard they were hitting hard at 2.5 MPH? Maybe the lure worked better at that speed? Brother-in-Law said that when they turned the boat they stated hitting on the outside lines, so they just increased their speed and did O.K. that day. That success could not be repeated.

We are running out 90 feet of cable on the Downriggers, figuring a 45 degree angle while running at 2.0 MPH, but we don't have a clue if we are right!

We have been running 120 feet of line out from the Planer Board line using Dispsy's (at 2.0 MPH), but we talked with one guy who said "Nah, you gotta' run 180 feet of line." We might try a sinkers instead of the Dipsy's next time. He has one 3 oz. sinker that runs a wire up from the eyelette in front then back ending with a swivel, but can't find that one like that anywhere.

I think you have the picture that we are not certain what is happening under the surface, and would sure appreciate any suggestions here. Beyond that does anyone know of a web-site or printed material that explains these things?

theres a book i think is called precision trolling not sure by who but it is the bible of trolling,i think its avalable at just about any sporting goods store,probably most big bookstores too;)

The precision trolling book is a great reference book that gives you a starting point. If you are really interested in seeing exactly what depths your rigs are running at, then set out looking for a flat piece of bottom w/o structure at your desired depth (ex 80 ft). Start your troll at the desired speed (ex 2.0). Then take the hooks out or bend them so they do not work on your plug or harness and lower your downrigger (this keeps you from getting snagged). When it starts bouncing off the bottom, raise it one or two turns and look at your depth counter on the downrigger. Mark this depth down and compare it to your fishfinder. Do this both into current and with current. Mark these depths down as a reference for later. Do this again at a faster troll speed and other depths. Once you compile enough info, you have your personal precision trolling refernce book for your setup. Sounds like a lot of work, but the info is exact to your style of fishing. No more guessing and trusting others guesses.