Oceanis 45 water tank exchange for fuel one

[Opty]

Has anybody tried to exchange the aft water tank for fuel tank?
Does it need replace or can be it be filled up with diesel?
I mean the tank reconnected to fuel line of course.

 

[Barryr8195]

Do you already have a second fuel tank? Beneteau installed the second fuel tank (19 gallons) on the port side, aft end.