Well, I've seen that done at our marina at least a couple times, bolted to the swim steps or even on sailboat transoms to replace dead inboards. I know it's done, but it always seemed like a -- hideous jury rigged? -- okay, I'll be nice, an in-elegant way to replace dead engines. I'd be interested if anybody did it on purpose though, in other words, to actually improve efficiency and maintenance access, rather than as a lower-budget means to replace dead engines. But then I have pretty limited exposure to boats here, maybe that's much more common than I think. Fuel lines, steering lines, ignition cables, beefing up the swim step struts or transom, conversion of a diesel fuel tank to more likely gas for the outboard(s). Hard for me to envision that it's cheaper or better in the long run. I'll be interested in the responses to your post though, maybe I'm out to lunch and it's commonly and neatly done.