Lund Pro V Livewell

I have a 2005 Lund 1900 Pro V SE. I am trying to figure out the livewell system. I think I have the valve selection from Recirc to Fill etc figured out but my question is in the well itself. Do both holes in bottom of the well need to be plugged for use or is one an intake for the recirculating? I’m not sure if I need a plug in pipe overflow tube in one as well. I’m also trying to figure out if I need a plug in the livewell drain at bottom of transom when boats in use or does that drain need to stay open? Thanks in advance!

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One of them is for the water depth tube.

Any idea if it’s the one towards the stern or the one towards bow?

I believe it doesn’t matter as long as both are the same size. The water overflow tube is just a piece of PVC pipe with one end shaved down so it fits in the drain hole. The other hole is for the drain plug. Both holes drain to the same place, so at least on the 1900 ProV I once had, they are interchangeable.