I am looking for a 10-14 ft jon boat.  I hear all these numbers such as 1232, 1236.  I am assuming that that means 12 ft long and 32 or 36" wide.  Where is the width measured from?  What the minimum width that I should get if I plan on adding at least a deck up front.

Andy

You're right. The first number is the length, the second is the width measured at the widest part of the floor.

The wider the boat the more stable it will be.  If you are adding a deck, you will be raising the center of gravity and making it less stable than if you stood on the floor - so the wider the better.  Also, the more weight you add the lower the boat will sit in the water and the less freeboard you'll have - something to consider if you will be fishing around bigger boats that throw wake, or in rougher water.    

It really depends on what you are comfortable with.  I've seen very nice 1236 boats with decks.  Personally, I have a 1548 and I use mine on ponds, larger lakes and small tidal rivers and it does very well.   Persoanlly, I wouldn't go smaller than a 1448.  But I admit I've seen very nice smaller boats that do exceptionally well.