Leak in live well/ overflow tube

[Tr91Mako231]

Hi guys, just completed replacing all the tubing,fittings and pumps for the livewell and raw water wash down. Checked all the thru hull fittings and all appear to be good. This summer I had an instance where the bilge would kick on every two minutes or so. Guess two to three gallons minute into the bilge. I capped off the scupper for the livewell overflow and no one water in the bilge. So now with all livewell fittings, tubing and pumps replaced, Ive narrowed the leak down to the livewell tank itself (which I doubt), or the livewell overflow tube, fittings or overflow scupper.

Any ideas on how to check these? The overflow drain is foamed in so thats a problem.