A gallon a day? :-0 That's a large quantity of water to be coming in with the boat at rest.
If it's an inboard engine, the stuffing box would be an immediate suspect.
Otherwise might be a broken hose at a seacock. If it freezes in winter where you are(I don't know where you are) then a hose may have burst or popped off the seacock a little.
If the water is dark it may be rust - check the bilge above the keel.
If it's coming in at rest, consistently a gallon a day, then it's not coming through the decks, so no wood to pass through, unless you have a less encountered cored hull.