Gem555,
Hopefully the fine folks here haven't made you leave in despair. I know you were just looking for recommendations of someone who could make your A4 all better, and instead you got lots of DIY advice.
I fully agree with what everyone is telling you, if you want to enjoy your older A4 powered sailboat, and ~$15K for a diesel repower isn't in the cards, then you really should learn a bit about that engine and get your hands dirty.
But ... a third option is to just find another good A4 out there and do an engine swap. Fortunately, the Catalina 30 is about the easiest boat to do such a swap in. Find a good running, or freshly rebuilt A4 and have your boat yard swap it in.
Oh, lookee there, a rebuilt A4 in your neck of the woods for $2500:
https://maine.craigslist.org/bpo/d/r...576861602.html