I have a 1982 Hunter 25' which I race/cruise and love. Fast, solid boat! However, nobody could pay me to own a new Hunter 25'. Poor construction and more for a housewife to putter around in.
Two great questions! I myself just bought a Mercury 9.9. This is PLENTY of engine. I almost went 6hp, but if you are caught in a storm you will want that little extra. Do not go any higher! The dry weight is 93lbs. My old 9.9 was 78...I believe. I was a little concerned to I put new bolts/lock nuts along with very large washers, along with another set of washers to offset the weight (Hunter only puts 4 bolts with 4 little washers. I was totally not comfortable with this.) The only problem is there is a gas tank shelf and you have squeeze between into the bilge to get to the lower two bolts. It was very uncomfortable to do, but my mind is totally at ease now. I also made a new
engine mount out of 3 pieces of 3/4" oak ply (gorilla glued it, sanded and varnished it with 3 coats of man-o-war high gloss. Looks great!
Now...more important, the crack in the keel. It is normal to have what may look like a seperation. The question is, are there water stains that look like leaks? If not you might be halfway home. Second, go onboard and lift up the bilge board in the main salon. You will see, I believe 4 keel bolts. If they are rusted to hell then move on to your next possible purchase. Otherwise, throw a coat of ablative
paint and set sail. You might notice that water will fill that bilge where the keel bolts are. Don't worry, that is normal. That is coming from the percperation or other areas of the boat, but settles there because it is the lowest point of the hull.