Brass splashwell drain tube removed. I used a hacksaw blade and cut three slits (through the tube lengthwise), then dented one edge in with a cold chisel and grabbed it with vise grips to pull it out (not hard since it was barely sealed).

Drain hole after tube removed. Dry (balsa) core, thankfully, although there was only the bare minimum of sealant and no isolation of the core.

Transom side of empty hole. What you are seeing is the balsa core of the transom, followed by the forward fiberglass skin of the transom, and then the (white) filler that fills the gap between the splashwell molding and the forward transom skin.

Filling the hole. First I used a dental pick and a Dremel tool to remove the core for a good 1/2" beyond the drain hole. Then I enlarged the hole in preparation for inserting a 1" ID (1-1/8" OD) fiberglass tube. Then final sanding and cleaning, and I put a good coat of neat epoxy all around the hole. After that (and will the tube prepped), I slowly built up the hole with thickened epoxy (colloidial silica). I had to do it in layers so it would not get to hot as it kicked (but all in the span of a few hours so it was still plenty green for a chemical bond).

Bringing the fill up to the proper thickness. After this I overfilled it a bit, and then "buttered" the tube so that it would "squooge" into place with plenty of epoxy all around.

The tube bonded in on the splashwell side. I inserted it from astern just to where I wanted it, and let it "run wild" on the outside, to be cut off later. This made it easier to work with than a just-right-sized tube.

"Impalement patient" as the epoxy cures. I let it cure for a couple of days before trimming it.

After a couple of days of curing I cut off the excess tube and rounded over the after side. Then I prepped both sides and ran a fillet around the outside of the tube. Next I'll sand it and I may trim it slightly shorter on this (splashwell) side. I'll let the fillets cure for a longer time before ultimately gelcoating things. Hmm, I'll have to add a photo of the after side too.

A perfectly circular crack in the the center (athwartships) of the splashwell gelcoat turned out to be a "phantom" drain that had been drilled for but then simply filled and gelcoated over, presumably at the builder or dealers. Subsequent conversation supplied me with the info that the center location was typically used for twins (my boat has two engines, but not twins). This type of "repair" (just filler and gelcoat) is destined to crack, which it had. I ground it back in a taper to prepare for adding fiberglass cloth. Actually here I had taken away too much of the fiberglass (pink bits) and so ultimately I increased the diameter and improved the taper (leaving more glass to bond to), but I don't have a photo of that. This gives the idea, anyway.

Here I have fiberglassed over the depression. I started with neat resin, then leveled the center with thickened epoxy (colloidial silica), and then added concentric layers of 10 oz. cloth. I added some peel ply (release cloth) over the top to smooth it - that's the "windbreakery" looking stuff you can see. You can see the "real" drain over to the left in the photo.

After removing the peel ply but before fairing, etc.

Transom side after filleting but before sanding or gelcoating.

Through hull

Splashwell drain, finished, inside

Splashwell drain, finished, transom