upthesaukee
I think that you're referring to marker #75 (the flashing light outside WAM). If so, the coordinates I use are N43 32.831', W71 17.593; they can be entered manually.
There's a wealth of waypoint info on the back of Bizer's map of the lake. It's well worth the time it takes to enter key waypoints into your GPS; or, you can buy an electronic waypoint file from them at a very reasonable price and save the manual entry time!
Silver Duck