For what its worth... I just bought an ERY32521M77B. Among other things the prop was a question that I brought up when I was doing maintenance in drydock this month...
The boat originally came with a 2 bladed prop which was replaced with a 3 bladed prop by the former owner. From previous experience I didn't like the effect of the pressure exerted on the rudder by the 3 bladed prop. So, before changing out the 3 blade to a two blade I consulted with Willmington propellor service in Willmington, Ca. They said "if your going to do any long haul motoring, and if you want control and maneuverability docking and what have you, the 3 bladed prop is the only way to go...
Jim Weatherbie