I looked at doing that when I had the boat. If you've still got the stock valves and single pump, anything is worth the upgrade. I replaced that same system in a couple customers' boats and it's a big difference. Not sure what the Gravity 3 consists of, but in those boats I installed 3 jabsco's, each having their own 1" intake from the bottom of the boat, and each had their own switch. Give me a call if you need some help with it.