The AC130 is awesome, but these Navy ships have something even better against small boats....
https://www.youtube.com/watch?v=lrre7STy5Pw
Meet the Phalanx CIWS
CIWS is pretty awesome.
It is capable of taking out supersonic missiles, so it almost takes all the fun out of the near stationary target a small boat is... Too computerized...
How about getting a few Miniguns on the rails and let the crews have a little fun?