See the attached photo- this is what your canoe had originally, though it's odd to see two of them mounted to one deck... maybe the previous owner moved the position at some point, or maybe the canoe just wanted to show off with TWO painters. The assembly in the pic was purchased directly from Old Town. I can't get to a canoe with an old one on it right now, but they're the same. You can see that it requires two holes to be drilled, 1/2" apart. The large leg is about 3/16" in diameter. The wooden piece is just a block for underneath the deck.
Michael