I have a 14' jon boat and am thinking about doing a conversion on it like I've seen on YouTube where plywood and 2x4 are used.  I realize this makes it heavier so would that stabilize the boat so that it doesn't rock so much?  Also, right now I have an electric motor so would the added weight be too much for an electric motor?  I have also considered using PVC pipe on the sides to stabilize it.  Your input would be appreciated since this is my first boat. 

If you add weight higher than the bottom of the hull, that will make it more unstable--simple physics.

Check out tinboats.net. Read all you can and look at other peoples modifications. Then you will get a good idea for yours. That site is priceless when it comes to modifications. I must have looked at hundreds of user posts before I even began mine. Once you get a game plan, it goes much better! Good luck and show us what you do!

Dyerbassman - you were right about tinboats.net. Spent the night reading and looking. Thanks for your help. I'll let you know what I come up with.