Here's an article that makes interesting reading.
Note the differences at cruise rpm, not full rpm, they're pretty close. Not as quiet though, but that can be addressed with acoustic foam. Doesn't cost 7 grand either!
I'm pushin' retirement age. Construction is way down, so I decided to build my own boat with a nice outboard. I started looking at this one add for a "1966 Bearcat 55". I had never heard of these engines before. So I started doing research. I was glad I did. They're not only easy to work on, but, it's also the nostalgia. A great piece of American history. But, before I forget, I want to wish all of my "boating buddies, buddettes" and fellow veterans a happy veterans day.