There is the purists dark side. My 1936 wooden power boat is quiet enough to carry on a normal conversation at wide open throttle. That comes from two things. First, I paid a lot of attention to sound dampening when I did the engine install. By that I mean that all the openenings into the engine space (required for air entry) are baffled and everywhere else there is a 2" layer of sounddown. The second reason is that my 32' boat has a 40 hp diesel. I still cruise at 7 knots on 2/3 gallon per hour, 5 knots at 1/3 gph and can hit nine knots if I want to (2.5 gph). Of course I have the sailboat too for those windy days