Thinking of switching from a b1 to a b3. Would I use the same pitch on the b3 props as I had with the b1?

Your boat's size and motor will determine if you will run a 2.0 or 2.20 Bravo III and that will dictate what prop set pitch you will go with.

There are 4 B3 gear ratios to work with and will need to be concidered with the change. Also, taking into concideration what you currently had for set up and performance numbers.

To sort of answer your question, if you were at the top of the recomended rpm range with the B1 set up, you will probably be able to use the same pitch going to the B3 set up if the gears were the same. But as stated before the gears are different. B3 props are truer to pitch.