I removed all the fittings from the deck and transom as part of my balsa core repairs. This is just to show how I removed the splash well brass through hull fittings to check for rot. I used a cold chisel to tap the lip in. First, at 90 degrees around the edge to form a four leaf clover, then an eight petal flower, etc., until the lip is pushed inside of the hole.

Then you tap it out and into the splash well. Both of the drains had a skim coat of caulking and there was no balsa damage.

The hole was hogged out, filled with epoxy and microballoon putty, then a larger PVC thin-walled DWV pipe was inserted and trimmed with a flush cut saw. The cream colored PVC matched so that no gel coat work was required. Although the opening is only 3/8th inch larger, it can flow a lot more water and sits 3/8" lower in the splash well.