For those of us who can't afford $10,000 to upgrade to a diesel, and want to keep our Atomic 4, and have a feathering propeller, the folks at PYI can accommodate you.
We have a 1975 Pearson 10M with an Atomic 4 direct drive. Using Indigo Electronics 10x7 three-blade propeller as a yardstick, PYI took their 12 inch three-blade classic, cut it down to 11 inches. I set the pitch to 7.4 (18 degrees), and now have a propeller that backs up as straight as your car does.
It feathers, increases speed under sail, and forward thrust is definitely as good and seems to be smoother than the old 12x7 two-blade that most Atomic 4's come with.
My Atomic 4 is equipped with a 5/8 shaft, 3/4 taper, and the new MaxProp was basically a bolt-on affair with the exception of having to shorten the threaded section of the shaft, easy to do with a hose clamp, a hacksaw, and a file.