Now you've got me confused. Are you using down scan or 2D because I don't get a picture until the rear of the boat passes over the object and if I waited until the pic was off the screen, I'd miss my target a long ways. I generally pitch my bouy over the motor just as soon as I see the object appear on the screen.
Sorry, I may have been unclear. Wait til you see the brush pile end, this is usually when it disappears for me because I keep my gps/sonar split and on a 5" screen, there's not much room!
Like in this pic, I would have thrown the buoy right when the pic was taken.