Re: 79 tri hull project with ?'s
I found this article for you. It may explain better than what I can. Hope this helps.
1. You need one thru-hull livewell pump, one tube of 3m 5200 marine adhesive sealant, a length of hose, and a sprayer bar. A SPST switch and some 14 gauge stranded copper wiring. And a fuse (and fuse holder, unless you have an open slot in your fuse box).
The pump intake is a threaded pipe that goes through a hole in the transom, with a large pvc nut that screws on the outside and holds the pump in place. Seal the hole with 5200, inside and out. Cut the excess off the intake pipe with the pvc cutting tool of your choice.
Clamp the hose onto the pump discharge outlet, and route it to the livewell where it won't get in the way (under the gunwale works fine). Mine has ordinary garden hose -- it's not a hi-pressure application, doesn't have to be fancy. Most livewells have a sprayer bar, to further aerate the incoming water.
My livewell overflow drain is just a hole in the side of the boat (a few inches above the waterline). Others utilize a standpipe, with a drain hose running under the floor to a thru-hull fitting in the transom. Water enters the livewell thru this hose whenever the boat is floating, but it only fills up to the waterline.
Your livewell should also have a drain, through a hose similar to the overflow standpipe described above, or if it's like mine, it's a hole in the bottom of the livewell (which is also the bottom of the boat.) I also have a submergible pump-out pump in the livewell, so I can pump the old water out while pumping fresh water in.
On the pump, the black wire is ground, connect it to battery negative; the brown wire is 12V -- connect that to one pole of the switch; the other pole is connected to battery positive (thru a fuse).
You can run the pump continuously, or run it for a few minutes every half hour, whatever, depending on how much fish you have on board, and the water temp. More often in hotter weather. On really hot days, you might need to drop some ice in there ever once in awhile.