Converting A Fish Box To A Live Well ??

Water flow and discharge....my preference was always to keep it above deck where it is easily monitored and maintained. Consider an under-chair setup? Otherwise a "portable" tank that can stow in the deck fish box when out of use? Tap to a salt water deck wash pump...?

Not sure how much you fish but the on deck poly live wells are hard to beat for cost and convenience. I keep mine inside one of my (huge) deck boxes and only hook it up when I use it. The rest of the time it’s out of the way. I’ve had below deck baitwells before and they were nothing but trouble. Hard to access the baits, can’t see the baits when underway, and if the macerator fails you have a huge mess on your hands and it’s hard to get the water out. I’d love to have a transom well glassed in with a window but the next best thing IMO is a light weight one on the deck you just have out when you need it. I have the 26 gallon Moeller but they also make a 40 gallon and if you need bigger there are some really nice fiberglass ones that are still light enough for one person to carry on and off the boat.

I have a dual purpose saltwater wash down/livewell pump but I don’t recommend that. You really want a low pressure high flow pump for the baitwell and the opposite for the wash down. I plan to change mine over to seperate washdown and baitwell pumps - can hook them up in series to the same thru hull. Lots of posts online of how to do this if you search.

For the over board, the quick and easy and temporary way is to run a large drain line on the deck out of the scupper, ideally out of the way under the gunnel, but can also run the line below the deck to an overboard discharge thru hull/drain and add a flush fitting on the deck for the baitwell discharge to connect. The latter is how a lot of the big sporties in palm beach have their on deck baitwells set up for sailfishing. A lot of them have two tanks for different baits.