As someone who runs a 14(deep V however so probably heavier than yours) with a 9.9(4-stroke mercury bigfoot.. so heavier than your normal 9.9) I would tend toward more power. A friend runs an older 20hp 2-stroke johnson on a 1442, it scoots with 3 of us in the boat. My 9.9 will plane out with 2 guys, or 1 guy gear and a dog, but with three guys or even 2 guys and gear, its quite slow. All depends on the budget as well!
the biggest its rated for. I had a 1436 War Eagle with a 35. Not something i would do on my own but i bought it used. it was scary fast. same boat with a 15 was great with on guy, two it started to plow. Went to an 18hp tohatsu and it was night and day. granted your boat is probably lighter than that war eagle. I would go with a minimum of a 15 but definitely get bigger if you can afford it. If you're buying new look into yamaha's new 2-cylinder 25.
My main criteria is going to be ability to start in very cold weather. I don't want to drain the battery or get a coronary pulling a starter rope. Preference to fuel injected electric start over HP. 18 - 25 HP would be ideal. The Yamaha F25 is superb.
I had a 1970 something 14/36 sears that was made out of tin, thinner than your aluma. I had a 16 h.p. vanguard longtail on it for hunting until I bought a prodrive boat and motor. The longtail 16 had pull start and electric. Still have the Sears with a 9.9 2 smoke on it. The longtail worked great and the weight of the motor was more inside the transom and you drive from almost the middle of the boat, so it balanced out very well.