The second one from left to right is the only one I'm currently plugging. Is it alright not to close the other three? 

[![holes][1]][1]

The boat hull is MAKO 86 23 feet . The boat is not currently sinking, but every 10 minutes I can hear the bilge pump pumping water (Like a jar of water) outside the boat. This is all new to me. I only know is that the second hole must be plugged before going to the water, but what are the other three for? 

It is an outboard , center console and it also has a living well. I never use the living well. It always empty. The one I plugged each time I go into the water is the bilge drain. If not plugged the boat would sink. The other three I believe are called thru hull fittings. The other three I don’t understand the usage of them, I'm also suspecting that water is coming through them into the boat causing the bilge pump work every few minutes

  [1]: https://i.sstatic.net/TjHbz.jpg