Often, the leak in livewells is around the TOP of the livewell. Often, there is NO sealant there.
So you either have to stick your head in and look UP at the perimeter, or use a mirror.
This is a trade-secret, I usually don't tell this, as I make money from fixing boats. The trick to fixing the problem, is cutting the correct size tip hole in the tube of sealant, and making sure the area is really CLEAN, before applying the sealant. 5200 is very permanent, but pure silicone works well, too, if the area is clean and you know how to tool it.
-TH