The only complicating factor in your case is how close the damage is to the transom. Chances are that given the age of the boat and the location of that damage, you are going to have to replace the transom anyway, so you might want to wait on doing the patch until you have total access to that portion.
I'm thinking hollow point since it didn't penetrate very far. I did pick it up from the hood so that may explain it.Thats a 9mm GSW you took there in the starboard corner! lol
Nothing more expensive than a free boat, but that looker is worth all the aches, pains and dusty lungs!