The screw holes could definitely be it. It could also be the sealant around the drain for the livewell or the bilge. It could be the live well leaking into the bilge area.

There are a couple of easy ways to try and figure it out. First off, be sure your bilge is dry, and fill the livewell up with water. Check the bilge area a little later and see if there is water present. That tells you if it's a leaking livewell.

Another is to pull the boat out into the driveway, put the plug in it, and fill the bilge with water from a hose. Be sure to fill it with enough water to come up to the water line when the boat is in the water. Look for any water coming out of the boat, and you've found your leak.