yeah if the bottom is very clean and the sea very flat and the boat very empty, dirty bottom, medium seas and full boat, prob about 500nm with a small reserve, we are about 13 metric ton laden .
13 ton boat with 280 l of fuel and 4jh3e= 500nm doing 5kn,6kn=400nm,4kn=almost a 1000nm with slightly dirty hull
, a very clean hull
and glassy sea add 30%, rough seas and headwind subtract 40%.
We have used a tank (280l) going less than 250nm motoring into f7-f8 and 5-7m seas at 4-6kn but we have also gotten 800+nm motoring slowly in calm conditions.
So factor 1NM per litre in the worst conditions and 4NM per litre in the best conditions