I bought a Bass Tracker Pro Team 175 last year with a Merc 25 horse on it. It is rated for 40-75 horse motor, but what do you do when you find a nice boat with all kinds of gadgets, a trailer, gps, downscan, and lots of storage for $3k??
So I went for it, and with myself, my wife, and two boys, we top out at about 25 with the right prop. I have found it to be perfectly adequate for me. Obviously a 70 would get me to places a ton faster, but I have never once felt frustrated or slow on it. I get it closer to 30 when I'm out alone.
Hope this helps.