A 23ft boat with a 175 2 stroke Had to be a PIG.
A DF250 would be a MUCH better choice. Just because you have the Power, doesn't mean you need to use it.
Yes I know this is not the same.... But it's a example. I have a 2072 SeaArk. [Giant Jon Boat] It was powered by a 90 2 stroke. Once I dailed it in.... It would Top out at 34.6MPH it got 3.5MPG on average.
It's been Repowered with a '23 DF140B. It will top out @ 42.6MPH it gets 6.5MPG on average.
The new engine with Higher power typically cruises at 3500. For 20+ MPH . It will cruise @ 4000 for 30MPH.
It's not run fast, as it is a BIG flat bottom boat and conditions don't allow for speed.
I would guess you are getting 1 to 1.25MPG right now with the 175. You will get 2.5MPG at least with the 250.
A BIG inline 4 cylinder engine is not enough for that boat. Thats what the DF200 is.