The Atomic 4 that came with my 1977 Ericson 32 has been a pain in the rear ever since I bought the boat 2 years ago.
Define "pain in the rear." Properly-maintained A4s that aren't sick in some way tend to be quite reliable. The A4 on our '76 Pearson 30 runs like a top. (Knock on wood!)
Any thoughts on the pros and cons of rebuilding the Atomic vs. replacing it with the Yanmar would be greatly appreciated.
Check this thread: Replacement - Heresy?
for a similar discussion.
Personally, as I noted there, I'd prefer to keep the A4. I prefer gasoline-powered engines over diesel.