Old tube, beginning cuts. I made them with a hacksaw blade.

Old tube, last cuts. I got nervous at this time, because as I got close to all the way through the 6 o'clock cut, water started to lubricate the saw blade. Uh-oh.

Old tube, section tapped down with cold chisel, after which I grabbed it with vise grips and pulled it out.

Old brass transom drain tube, removed. As you can see, the sealant was scanty at best.

Tube removed, some core dug out. There was moisture in the core for around a 1"-2" wide area directly beneath the tube, but after that all was dry, thankfully.

Tube removed, inside view (upper left corner). The smaller holes are where a bilge pump had been fastened with screws. Even though this "sump" area is depressed, there is still core in it. Luckily it was all dry. Here I have enlarged the holes slightly and dug out a bit of core all the way around. I then filled them (and then later cut the whole area out, but that's later...)

Damp core. It could have been a lot worse.

I temporarily moved on to another task because rain was in the forecast. I didn't want water to get into the core, so I used butyl tape and some large fender washers to make a tightenable plug.

This is the inside of the plug. It was in place for a couple of weeks and quite a bit of rain (which I bailed/pumped out, but which did get up over the plug at times). I felt pretty good about it but still had my fingers crossed when I removed it - the inside was bone dry and there was no sign of any water penetration whatsoever. Whew!

View of original sump at transom.

Beginning cuts.

Upper section with core removed.

Some of the removed core, dry.

Section of removed core and inner skin - all was dry and well bonded.

Mostly full cutout (I did a bit more cutting out and shaping in the after corners of the sump after the photo was taken).

Stack o' cloth

Wet out and filleted.

Fiberglassed.

Fairing applied.

Fairing sanded.

Coat of white-pigmented resin applied (it's normal for the pigment to be just sort of a "wash" of color like this, vs. a solid color). As it turned out, I later removed this coat.

Pigmented resin coat removed; small holes drilled to drain nuisance water until I re-drill main drain hole.

Marelon garboard drain fitting.

Another view of the Marelon garboard drain fitting. The threaded plug is made of slightly softer Hytrel™ (Dupont).