14' Lonestar Project Boat

[roofus]

I have a 14' Lonestar that I am trying to "restore" I basically want to replace the floor, put in a couple of seats, paint it, and power it.
All I want to use it for is fishing. I tried a small alluminum boat but that was a little scary on the bigger lakes so her I am on this project.
I have removed the old floor as it was rotten and I had to make a repair to the middle stringer that the floor was attached to, no problem there.

There is NO floatation foam in the boat anywhere and the boat has no motor.
The guy I got it from said it had a 50 HP on it. I was thinking more like 15-20HP for my purposes.

Do I need floatation?
How do I know what size motor to use?
Can I cut the top out of the closed hull and replace it with a small casting deck?