Drill a Hole
By sounding the hull with the handle of a screwdriver, I found what I believe to be the lowest part of the bilge. Note its position approximately 30 inches ahead of the shoe that supports the bottom of the rudder.
I had to drill the hole last fall after the boat was hauled before the freezing weather started in earnest. As you can see, there was a bit of oil in the bilge that has stained the bottom paint and base of the cradle.
The next step was to take a small router and mill away some of the fiberglass so that the hull plug could be flush mounted.
Install the Fitting
Once the routing was complete, the drain plug assembly was caulked and bolted into place. The most difficult part of mounting the plug was for the lucky person chosen to hang upside down in the bilge to hold the nuts while the fitting was screwed down.
What was even worse was doing it a second time when a leak was discovered in the caulking! The integrity of the seal was checked by filling the bilge with about 12 inches of water. Laundry detergent was added to the water to help break up the remaining oil in the bilge and to clean it up a bit.