Volkswagen Marine has developed a range of
diesel engines for boats from 40 to 370 hp.
For example, the Volkswagen Marine Power
is chosen even by many commercial users,
sailboats and motorboat owners,
Volkswagen TDI and SDI marine diesel engines
are equipped with ZF Gearbox, Turbocharger from
BorgWarner or Garrett, and marinised by Mercruiser.
They are very economical and you can get
parts at any auto parts store
(meaning that's a significant savings)