I hear alot about people wanting to use VW diesels in their boats.There was a company that use to make kits,but VW contracted with a company to build the marinized version.It is very expensive to buy one or to purchase the parts.This guy did it and so can most mechanically inclined people that understand water cooled marine exhaust systems.I wanna do a few just for the experience.

Marinizing VW turbodiesel engines - Boat Design Forums

 

Either a keel cooled heat exchanger, or a water cooled one and a water injector just post turbo to keep egt's out the exhaust down