Jimmy there seems to be some controversy. Many marine engines seem to use a chain drive just like standard engines, which of course means the cam is ground special.
I'm not a "boat guy" and have not figured out why some reverse engines end up in single engine boats. Maybe it's as simple as some manufacturer "overordered" on LH engines for twins, and got rid of 'em in single engine installations.
I don't know.....maybe there's some advantage for some uses, approaching a particular side of the dock with a current running? Don'..................kno................