Not to be rude, but weight is a factor
A 3 hp motor will move that boat boat close to hull speed. The problem is that it is hard to get a long shaft under 10 hp.If you can live with moving weight back, it will be much more cost effective.The other option is find someone changing out there old adjusable mount and install that. I would try the boat first.Sorry, short on time if you need more info ask again...hope it helped,r.w.landau