Hack, your boat is like this one? https://forums.iboats.com/forum/owners-groups-by-manufacturer/s/starcraft-boats/648918-1974-starcraft-16-ft-super-sport
In my youth I used my dad's 5hp motor on camp and rental boats, bare bones aluminum ones, 16 footers, I wasn't going anywhere fast, but it beat the heck out of rowing! Just my view? For a boat as pictured a 9.9 minimum? The boat pictured has to weigh x2 of those camp and rental boats?
Not sure how slow you really need to troll, I trolled for walleyes, pike, smallies with my 35hp Merc on a 16'8" side console and speed was never an issue, with a 60hp or more maybe?