I am unclear on what you are asking, but I did install a 30 gallon Offshore Products circulating bait tank in my 1801. We did the following:
Drilled a through hull and fitted a bronze ball valve topped by a two way - one of a raw water pump, the other for a bait tank pump.
Installed a 850 GPH Rule bait pump. Wired the bait tank to one of the open positions on the factory switch panel.
Plumbed the bait pump under the deck to the location of the bait tank using 3/4" tubing. This uses a through deck water tight fitting.
Plumbed the tank overflow outlet under the deck to the transom sump using 1-1/4" tubing. This also uses a through deck water tight fitting.
Fitted a 3/4" Starboard ring the the deck to fit the inside bottom of the bait tank. Fastened with 12 stainless screws and sealed with 5200.
Mounted the bait tank after completing the hose hook-ups beneath the tank.
This tank / pump combination completely replaces the tank water every 8 minutes and keeps bait alive for a long time.
Mounting ring:
Drilling for the through deck fittings
Finished tank in place: