I have a 2006 G3 CC DLX with a livewell under the passenger seat, directly in front of the console. It appears to have an overflow tube that empties through a through-hull in the bottom of the boat. I want to do away with the livewell because the space is worth more to me as a storage space. It's only a 16 gallon well. Any ideas how to seal the hole in the bottom short of welding a cover over it so I can remove the tube?

Why don't you just remove the tube and replace it with a plug, or cut the tube off near the bottom and place a cap on it?