OMC 800 sterndrive engine swop

Gentlemen the cost of gasoline (petrol) is rising so fast and diesel is becoming so popular here that I think instead of rebuilding my twin OMC 3.8 V6's with matching 800 outdrives, changing to diesel is the best option. I've just finished the refit of the Fletcher Zingaro 26 they're fitted to.
Although an engineer, I'm new to this. Which modern (and lighter) diesels which produce at least 170 hp would mate to the 800 outdrives. Would there be the possibility of marinising auto engines to fit - I understand marine engine camshafts differ to marine engines.
I would have thought the more modern diesel engines with OHC and turbo chargers would have been much more efficient (and economic at low speed) but although the present V6 engines are very heavy cast iron lumps, diesels with the same power might sink the boat!

 

Go to Lancing Marine in the UK. They sell complete engines, DIY kits and all parts to marinize car engines.