The main difference between Mercruiser props and Evinrude V6 props is the length of the splines in the prop hub. The Evinrude are usually shorter. I was able to drill out about 1/2 the splines on a Mercruiser prop and use it on my Johnson V6 outboard.
You might try to fit the prop to the MerCruiser and see if you just need a different thrust hub.
If not, I would inquire at a prop shop to see if the hub can be swapped over.