I had a 4 hp kicker on my 16' Smokercraft boat and wide open it would push it up to about 5 mph.
I also had a different 14' Smokercraft with a 15 and it would do ok with one guy, but still needed the fin on it to get on plane reliably and was pretty much a displacement hull with more than one guy.
It all depends on how fast you want to get there. If there is wind or current to deal with, you need more.
Typical boats in the 12-14' range will have at minimum a 9.9 and often a 15 or 25. I would consider a 15 the minimum unless I only needed to go a hundred yards and was never loaded with people, dogs or gear. 25 would be ideal.