Engine replacement
Paul, I have an A4 and I know the + of diesels, but I think the A4 is a jewell. If it threw a rod tomorrow, I'd rebuild or find another! What a cheap date. My friends with diesels ( used as sailboat auxiliaries) are almost always having problems and are spending far more time and $ than me, with less hours. Why? Diesels do not thrive well when run for short durations. I installed a gasoline vapor alarm & vent everytime. She runs like a watch and nothing beats 25 hp in the wind. Personally, I will save my bucks for other upgrades, since I motor just 20 hrs ? a season here on the Great Lakes. Just food for thought. I too have a beauty, a 72' with many upgrades, is and has been quite pampered. You may already be aware of Moyer Marine's site, they are a great source for anything related to the A4.
Good Sailing BN