Hi Two-Six!
Have you tried to set your engine setting to the lowest KF, and then hit the Back to base button? Boat use less fuel in this setting.
If you are so low this doesn't work, you can try Diesel-electric propulsion. Only use the diesels to charge the batteries and then switch to electromotoren when they are full.
Drive on the batteries to they are nearly empty and switch to diesel to charge, and so on.
Good luck!
