If you are laying up your motor-boat for a few months fuel contamination could be a real problem when starting up again.
Marine Red Diesel
Condensation in diesels tanks is the most common problem and it is
recommended to avoid any space being taken up with moisture all tanks
are filled for the lay- up periods. As , under
the tank with a drip tray or leave a 10 % clearance space at the top of
the tank to allow for expansion especially in the summer months. If
cruising outside the U.K. in warmer climes you may need to increase the
clearance space mentioned above to prevent spillage due to increased
expansion!
Conclusion
Near Full or empty is the best way to leave the tank when storing.
About the author