The diameters will be the same between A3 and A4 props when measuring small to small and larger to large. The pitch is higher with the higher numbers.
A series are for Diesels, thicker heavier blades. As far as I know the B and A series can be used on any 290DP or DPA-C series drives. I would stick with the A series if running diesels.
Each jump in number, example from A3 to A4, is about the same as 2 inches in pitch.
I have a B5 set on one of my boats, and with real-world performance numbers for RPM and MPH I have calced the B5 set to be in the range of 21-23 inch of pitch, with top speed numbers anyway. It is hard to gauge because with the 2 props it is like a variable pitch setup which gets you out of the hole strong but also supplies good top end.
.I have attached a Volvo prop guide in previous posts, I cannot seem to get it to work here. I will search for an older post with the guide in it. It helps some but in some areas it begs even more questions, sigh.
