when installing a 30 gallon day tank for my gen sets a few years ago, I was curios about the re filling methods available, settled on a dash mounted gauge with push button to activate transfer pump. Looking at Nordhavns they seem to have small daytank for the main engine, how do they refill ? seems they might get 4-6 hrs running before empty?
Most boats rely on an electric transfer pump. I'm not sure on the Nordhavn's and it's possible you could refill the day tank by opening a valve and gravity feeding it into the day tank on some boats if the other tanks are higher than the day tank.
CaptJ is correct, some but not all Nordhavns can gravity feed to day tank. An added advantage to this is it can allow complete draining of main tanks likley removing any water, sediment, sludge etc.