Another point is that the Atomic 4 is a physically lighter engine: I can just about carry one if you take the flywheel and the manifold off. Also, if you actually like to *sail* as opposed to motoring or motorsailing your sailboat, a gas engine is more appropriate than a diesel, which doesn't like to start in some cold, damp situations, and when started, prefers not to stop, i.e. you should really run a diesel at load until it is throughly warmed up. The Atomic 4 and the much rarer if similar marine gas inboards like the Vire 7 or the Palmer are low-compression engines that don't mind being switched on and off in ten-minute cycles, which is the usual time I find from sailing off the mooring and getting out into open water and motoring head to wind while I tweak the sails.
There is an extensive network of Atomic 4 diehards, plus the means to buy new blocks and completely rehabbed parts, plus aftermarket improvements. Lastly, they are simple to service. I took theatre instead of shop in high school due to the presence of easily persuaded girls in drama class, but I learned by rebuilding an Atomic 4 that I have delusions of mechanical aptitude. Now I've got a 52 horse diesel to play with, we'll see if I get chastised or not.
I do concur that diesels are more economical when doing a lot of distance, but with my Atomic 4, unless I go cruising down the lake, I have difficulty using ten gallons or 15 hours of running time a season.