I have been fishing for Lakers for about 3 years on Kensico. The only way I know how deep they are is with a fishfinder. You can pick up a portable Hummingbird for around $100 dollars or so and it will clearly show you the Lake Trout. A few days ago they were as deep as 100 feet. If you want to troll you are better off picking a depth ( with an educated guess) and then sticking to it. If you try to adjust the trolling depth in a rowboat you often loose too much time and then get hung up as the leaded line sinks to the bottom when you stop rowing. If you plan to jig or use bait on the bottom, the fishfinder is invaluable to see where they are and how deep they are. Good luck. Which reservoir are you fishing on for Lakers?
Tom