I don't often troll for Walleye but when I do, I prefer using lead core at 1.5 mph where each color will get you down approx. 5'.
Lets see, 125 yards equals 12.5 colors which should get you down 60 (+/ -) feet.
Yep, plenty deep enough.......
Disclaimer; not all leadcores are alike, troll responsibly. Also, use of lead products has been shown to cause brain damage.
What... Wait!!!