I agree with Klem's post with the exception that I still prefer a naturally aspirated small diesel. In larger diesels, such as OTR trucks turbos make much more sense where they need to generate 4-500hp with a minimum amount of weight. On most small (40' +- ) sailboats the weight savings is not a significant factor, and reliability is higher on the list of priorities. Turbos turn at up to about 75,000 rpm ( IIRC) and need a high volume of oil to lubricate the bearings and for cooling. While they are basically a simple device, they are an additional complication that is really not needed on a small, displacement style hull. In keeping with the KISS principle I would choose a NA engine over a turbo, but would not reject a boat strictly on that basis alone.
SV Laurie Anne
1988 Brewer 40 Pilothouse