the maximum displacement speed for a 16' boat is right around 5-6 mph, so with some more push you could probably go a little faster, but not much. anything more than that will take a lot more power and you'll start to come up out of the water. i don't think you would see much practical difference between the 80 and the 112 on a 16'.
https://en.wikipedia.org/wiki/Hull_speed
