That's why I like any semi-modern diesel engines built within the last 30 years, because they have FUEL INJECTION! No rusty or fouled or carbeurator to get clogged or flooded. Solex carbs are a P.I.T.A. to work on.
If I was shopping around for a used sailboat marine diesel for a C 27, my first choice would be a Universal diesel. The 5411 is cheaper, has excellent fuel economy & reliability, & its so simple in design. It should have enough oomph with its meager 11 horses to move the C 27 adequately. Its a lil mediocre for my bigger C 30, but couldn't part with this lil workhorse. The second choice would be the slightly larger M 18 Universal. Also a 2 cylinder, but with larger 18 horse dislacement. I also like Yanmar diesels as they're tough as nails. They also made an 11 HP model in their 2 cylinder GM series or the smaller but tough & simple YSM series. All good engines, & they don't even use glow plugs to start, just strong compression. The smaller Yanmar's can even be hand cranked started when their decompression lever is applied. Check around. Moyer Marine & Torrensen sell marine diesels used, rebuilt & new. If you can afford new, the Beta Marine models are built upon the Kobuta block, as are the older Universals.
Look around & my last advice is to stay small, as they will be easier to install, easier to service, more economical to purchase, maintain & have better fuel economy. If you have mechanical skills, then its usually cheaper to buy a decent used motor & rebuild it on a bench while taking your time, then install when you're done. So much easier to work on an engine when out of a tight boat. Try to buy the matching transmission with the motor. Universals use Hurth trans. that are also very tough & reliable. Good luck in the hunt.