So I have a 1990 nitro 175 tf. The livewell pumps and plumbing were completely ripped out. All that were left were the 3 way valves. I found replacement pumps but need to know how to run the tubing. It has two separate tanks, one nozzle for each tank, and both have an overflow. There are two valves that shut off from the lake water and make both pumps recirculation the water, does the nozzles that point into the livewell add areation? Do the valves opened that allow the pumps to pump in lake water keep water out while boat is in motion? Sorry for all the questions.

Also does there need to be a third pump?

Google Livewell Plumbing Diagram. It should give you some idea of how it should be plumbed 

Some have a fill pump, a recirculation pump, and a pump out pump, some only have 2....and some have just one pump and a gravity drain. I'm so confused lol

Yeahp with a two valve I dont understand how it works....the pump than can only recirculation or pump in freshwater....I would need a second valve to make it a pump out or a three way valve for it go gravity drain, also the stock valves are only two ways, the only thing left from the boat.....

Go check this out https://flow-rite.com/sites/all/files/file/pdf-marine/prod-livewell_control_systems.pdf 

Flow-rite's website also has a livewell builder where you can select the system you want and it will show how it's rigged up.

Looked at it, apparently I would need three way valves, my boat is factory equipped with two way valves....I give up boat is going to the shop. Be easier than guessing, or jerry righing.