I'm thinking she'll fight to get on top of the water, and if it did get on plane it might get real "mushy" if you try turning it too hard.
The standing rule is 75% of max for minimum which would put you around a 90HP. If you already own the 48, I'd give it a try. Nothing to lose there. But if you gotta' go get something, I'd look for a 70HP or so.
I had a 15' that was rated for 100HP. I ran a 50HP on it for a while and it would get up on plane with just me and a kid aboard, but add a second kid and it wouldn't do it. Boat was a little heavier than yours, but not too much - I think about 1,200 or so.