Well now when it comes to real Bar-B-Q and donuts, a man has no real limits other than when his wife says "That's enough XXXXXXX!". We have lots of posts about Manufacturer Boat labels and the like. Seems like the 16 runs fine on a 50 or even a 40. Perhaps a weigh in of the boat all up, consideration of the transom load of different motors, the distribution of fixed items and pax, the mission of the boat itself, the cost of a new motor/re-rigging, the availability of certain products, the fact that many motors are built on the same block and so it is just how they are tuned that produces claims of HP, the type of HP you want (torque vs hole shot vs fuel efficiency vs top end speed vs service life vs service intervals vs can you get the same result of a bigger motor with a proper Permatrim and/or Bennett Trim Tabs cs ETC ETC). Last but not least is re-sale value, some decisions pay off and others do not. Looking forward to you next post "I have decided to go for ??? HP, what brand of motor should I buy?"
Bob Jarrard
PS: Waiting for Doctor Bob to post, then I can rest my typing fingers. BJ