I am Japanese and living in Japan. But I bought a 9 yeas old sailing boat in Florida last month(Hallberg rassy 46) and sailed to Delawear.
For the next voyage, refitproject needs for her. I will across the Atlantic on 2014 spring.
Now the engine is Volve TAMD 31S with Aqua drive and 4000 hours 50000miles . Harldly used then condition is not so good. Smoke alarem will ring over 1800rpm may be becouse of blowbygas. Also noisy not only engine maybe shaft.
Aloha and welcome aboard!
Before replacing the engine I'd have a reputable dieselmechanic analyze the engine. There are oil analysis tests that can be done and lots of minor things could be wrong that will cause the engine to be noisy and smokey.
You may just need to make a few needed repairs.