Depends on the wind on the 500 type motor. One with a lot of turns can pull a prop that size direct drive, and assuming the pitch is no greater than the diameter (e.g. 1:1 or thereabouts) similar powertrain is fitted to the Engel Lafayette, and that nips along too- streamlined hull form.
Generally for a prop that size you shoud be looking at a prop speed of between 2000-500RPM, depending on prop pitch, speed you want, and running time. There are only a two or three companies I know of that make scimitar props, one is Raboesch, another is Prop Shop and I think George Sitek makes them too. Raboesch are pretty much all 1:1 or 1:1.1 pitch to diamter ratio. Prop Shop tend to be higher in pitch, so you usually need to dial the RPm down a bit. Don't know about Sitek props, never owned one.