livewell - my system
I built a custom livewell w/ epoxy & plywood into the floor of my starcraft cheiftan. It's oval, 4 X 1.5 X 1.5 ft & runs widthwise across the boat in the center; it's built right into the floor w/ a trap door & removable hinges. I think it's about 60 gallons.. Anyway, my original plan was just to fill it w/ a washdown pump (3800 GPH rule) and run an aerator to keep the fish alive.
This worked great, for anything besides baitfish.. so, to make it flow-through, I added a float switch at the top of the livewell and a pump to pump out, inside of the well. A flush fill fitting was also added to the top, so that the washdown hose could be neatly run inside.
Now, I just plop the filling hose inside the fitting, kick on the pump-out & washdown and when the well get's full, the pump kicks on and let's out a few gallons.. it fills up again, when it gets full the pump kicks on.. A system like this can be used for any livewell. Only thing to keep in mind is that the "pump-out" must be faster than the "pump-in". I've got about 15 ft of hose on the washdown pump, which slows the flow down so that a 1000 GPH works fine for the "pump-out".
The only downside to this sytem is it requires at least two pumps; which can draw some juice, as opposed to the more simple system of a drain near the top. The upside is that your livewell can be below the water-line, much safer for smaller craft - mine actually doubles as ballast.
Jon