Hi Lovey80
I managed 260L per tank.
We recently did 3 nights/4 days fishing off Breaksea spit with 3 on board and I took an extra 200L in a fuel bladder on the back deck as a safety margin - it was my first trip to that area. Doing the same length trip off 1770, i wouldn't bother with the additional fuel.
There is some video footage from our trip up there of a baby black marlin thrashing about the deck on top of the full fuel bladder... interesting few minutes that was!!! The marlin was quickly dispatched into the deep freezer, two days later it was nicely frozen
Ric