[jclark003]

Yes as I understand it the main differences are 3 blade props tend to be more efficient with less drag and 4 blade props tend to have less vibration and can create a little stern lift. May be worth bringing both sets to your prop shop. Tell them to tune the 4 blades to give you an added 100 RPM over your 3 blade setup (or whatever you are looking for). There is a lot of weight in the stern to lift so not sure how effective the 4 blades will be in that regard. There are a few 40 express members on this site. Maybe one of them can give you a little factual basis for changing.