thanks for all the replies. Here is the report I got from the last user
Port Engine Starboard Engine
Upon Departure - Sept. 17
Fuel Gauge Full Full
Fuel Top Off 7 litres 15 litres
Upon Return - Sept. 21
Fuel Gauge 1/2 Full 7/8 Full
Fuel Fill Up 38.4 litres 20.7 litres
My assumption is that the top off was till they could see it at the filler.
I don't believe they return to a single
fuel tank as this is a new occurrence. That and the tanks are 20 feet apart.
Ill check the fuel shut off valves to see if one is not open all the way but again I don't believe the fuel systems are tied together