Welcome! The 16's are great boats, but the factory just announced they are no longer making them so you may not actually be able to order one (see the current "End of an Era" thread). Therefore you'll likely need to find a used one, and most will have a 40 or a 50 hp.
With that said, I've run 16' Anglers with 50hp, 40hp, and 25hp. With one person on a lake the 25 did surprisingly well. But the Anglers plane pretty quickly and easily, and you may not have as good of luck with a 25 hp on a Cruiser. I certainly wouldn't recommend it, it was more of an experiment for me, and the person who bought that boat from me quickly changed it back to a 50hp as the 25 didn't really have enough power to keep on plane going over bigger waves and swells on saltwater.
If you're just on a small lake and don't want to get on plane, a 9.9 high thrust would probably work for puttering around, but would almost defeat one of the great benefits of a C-Dory, being able to get up and go when you want to! I usually prefer cruising 5-6 knots, but there are plenty of times when I'm glad I can also cruise at 20, both in the 22 and 16.
Good luck on your search!