Prop Size

Does anyone know what the standard size prop is for a 99 Outback with the standard stock engine? I have a 3 Blade and was considering a 4 Blade, but wasn't sure of the size.

Any input on Nibral versus Stainless? Isn't Stainless better, but less forgiving if you hit bottom? Also, doesn't 4 Blade offer a smaller/softer wake?

Thanks.