While never in one personally, I've worked on a couple and have a friend with one. Regardless of horsepower, I wouldn't go much more than 300lbs or so on the transom. Did some engine work on one with a OMC crossflow v4 90 which weighs almost exactly 300lbs and that was more motor than it needed, IMO
It's the typical old boat - heavy 4 stroke issue that just requires you to give up some speed for a motor with an appropriate weight or search out a good used two stroke. A OMC or Yamaha 70 triple at 240 ish pounds would be a really good fit for that boat or your Honda 50 which is one of the lighter 4 strokes in it's class right now at just over 200#
Flat bottom, relatively light boat - just does not need a ton of power to move efficiently. Have a 55 commercial Johnson on my (narrower) Pembroke skiff and it's more than enough power running 25+. My boat is narrower but laid up very heavy so I'd guess the weights to be similar.
Just my thoughts - hope it helps