On my 1991 StarCraft Eurostar 19ft boat there is a hole beside my drain plug. Would it be an inlet to something or outlet ? Sorry for the dumb question. I can stick a flexible wire in it.
If that opening is at the same level as the drain outlet, I too think it is for a live well, being an inlet. Otherwise an outlet would be well above the water line like R055 stated. JMHO!
Although, rethinking it, it could also be the live well drain once you have the boat home. So without pictures and more info, I honestly can't say.
As long as the hole on the inside is above the watwr level on the outside, water wont come in....
An overflow tube would raise the height of the interior hole even further above the water level outside.
As long as the hole is above the water level, any water that goes into the drain hole on the transom (your pix), it will drain out, esp if tbe boat is moving forward.
You don't want a live well just draining every time you are up on plane. You should be able to find the hose it goes to and find out where it goes. Most likely it is an inlet for the live well.
If you can see the inside of that fitting at the transom and there is no pump installed there, it is most likely a drain from a live well. The live well will have either a stand pipe fitting or a plug to keep water out or water in depending how you look at it. One great way to determine this is to pour some water in the live well and see what happens. If water pours out that fitting, then you have your answer. If you do see a pump at the transom fitting, then it is the inlet for the live well. Hope that clears it up some. JMHO!
So i'll be the first to mention this, no matter what the intended purpose of that drain/inlet is, its second purpose is to ruin your transom for you... At least from the pic, it looks like there is zero sealer and it is actually spaced away from the transom... That is absolutely letting water seep into the transom. (pic could be deceiving but it looks like an issue at first glance.)