Mazda has gone back to developing their rotary engine as a hydrogen fuel engine. Could we see the return of a outboard rotary as a emission free competitor for the 4 strokes? What about a rotary race outboard? Do you remember the first ones? The rotary engine has many advantages including lighter weight, fewer parts, and higher rpm capabilities. The Mazda open wheel rotary racing cars were successful. The statements presented by Mazda about the new rotary say it is much improved over the RX8 model. Time will tell.
History of the OMC rotary.
https://www.youtube.com/watch?v=SeomAj6QhvA