I tried researching this online. BAD MISTAKE.
You don't wanna know the search engine results.....

 

Boat plug probably would have been a better choice. Bet you got an eyeful.

 

 

Yes, my guess is that the drain hole the center would be or could be used as a passive drain.

 

Yeah, it will be the bottom center. Looks like someone has chewed it up pretty good with pliers or a channel lock or something.

 

Here's one that appears to be a direct replacement for the type you have:

Amazon.com: T-H Marine DP-1-DP Self-Retaining Boat Transom Drain Plug - Black: Automotive

 

Yeah, it came that way with the boat. I guess I had never seen one that threaded all the way in, so I was doubting it was the "boat" plug.

 

It is called a "drain plug" Butt plug has an entirely different meaning.

 

Bill Cosby turned his in yesterday, he don't need it anymore .....

 

Whoa whoa whoa I thought this was a family site, you can’t be airing that info out around these parts.

 

I will forever more refer to it as the transom drain stopper.

 

Next up, the pee hole on your motor. You know, where the water comes out!

 

...where is the location of my but plug.

Have you tried looking where it goes?
Just admit it, you don't know where your butt plug goes from a hole in the ground!

 

My daddy used to say I couldn't find it with both hands and a flashlight......

 

Your correct on the placement of the plugs, and if you have a hole in the side of your boat or the top portion of your transom is where the bilge pumps water out.