Re: XB2003/225 Merc Pro XS
If 21s can go 90 with 1.75 gears, and quick to 90 is the goal, and not topend...my guess would be 1.75s.....
I know before I had props made for the 21. The 21 ran 2-3 percent higher slip numbers in the prop slip calculator.....
For topend of course 1.65s...
Still have a lowly 2.5 so it's speculation on my part as well.