Automatic rough? Sometimes it's real.....
Joined this thread a bit late, but here goes....
Was returning to mainland after the Guernsey Rally. Just over Casquets when I felt a "nudge" in the engine. Asked my better half if she'd heard it - but no. Then suddenly it started to run really rough. Yes - she'd felt that! Alderney was in sight and we turned towards it, and as soon as within gliding distance, pulled throttle to save the engine (had previous experience of very expensive engine loss).
Glided in safely, and was left with the problem of what to do next as no-one available to help. Fortunately, phoned back to Guernsey and another rallyist could pick us up and get us back to Rochester. When we eventually returned and fixed the a/c, the problem was a rocker gear which had broken off, which meant a new cylinder. The other 5 had kept going until we decided to glide, but it still felt extremely rough.
Changed to a 4 cylinder Lycoming now, and by comparison to the Continental it feels relatively bullet-proof, and have no quandaries about launching over water, but am always aware and ready to react!