I don't think I could build a 20 footer that would handle a 175 HP, they are just too light and the USCG formula will not allow it.
Here is the link to the plans I am going to start with, before doing a bit of redesigning. Rated for 230 by designer.
https://glen-l.com/designs/hankinson/slither-snakeshtr.html
Also, the Coast Guard formula is null if you make it 20 feet 1 inch, as they don't place restrictions on boats over 20, like they do for ones under.