Realistically, 5-9 hp minimum, with 9 being the conservative pick. If you have heavy wind and current in mind, probably 15-20.
You will need a dedicated battery bank for a motor that size.
Only my opinion. Several members have installed gas kickers of various sizes. I’m sure you’ll get a range of answers. You need to bracket your performance requirements for a better response.
By the way, the outboard is the backup for the sails and vice versa. Once you get comfortable sailing, you’ll be able to manage if the outboard dies - subject to having some wind to work with, of course…
