It the boat is going to be light weight, then I would go with a 15" x 15" prop.
If heavy, 15 x 13" pitch. You want the motor to reach at least 5500 RPM at wide open throttle.
I carry three props for the 90, which is probably on the same block as your 75.
!5" for most sea level
13" for Powell, and very heavily loaded
11" for heavy loads at Powell, and lakes as high Yellowstone (over 7,000 feet).