I also have a 14ft jon with a 15hp. I use two 8lb mushrooms. Holds good when the wind isn't two bad. On a river or when it is windy it won't hold and I start drifting slowly. I was thinking of buying a anchor with a hook feature to use when on a river or in strong winds. But there is just not any room for such a large anchor so I will probably stay with just the 2 small anchors.
A 10 pounder should be fine for your boat, but what's also important is where you use it. Mushrooms are fine for sandy or muddy bottoms, but if the bottom is rocky, a Danforth is much better.
