New hole in the boat

[buckeye]

I need to add a bilge pump at the stern of my boat (it has two mid ship but none in the stern). I am thinking I would locate it out the side above the water line about 12". Does this seem reasonable? Any cautionary tips? Any reason I should NOT be doing this?

 

[Stephen]

Is it close enough to the other two holes to just add a third right next to them? It might look better than a single one in the stern.