In deck Livewell issue

[BoniB]

Just picked up my 74' 20SF and have been thinking about how to plumb the live well out. I have an existing thru hull with sea cock down in the bilge now that was used for a SW wash down. Since the thru hull is below the waterline and the fish box how well would it fill if I ran a line directly from the seacock to the live well? Then I would just use one pump to remove water. The livewell is on the small side and kinda squared off for using bunker but I would like it to be usable.
I'll probably end up using my portable 30 gallon round livewell; fed from the SW wash down pump and let it overflow into the motor well.

BoniB