when filling up leave ignitions on and you can see which is which.
if not sure then, start an engine and you confirm which is which as dials for that side will register /forums/images/graemlins/grin.gif
Came across a F33, when the owner left one engine running charging the battaries and walked to the club house and have a pint, while there got called back by a very /forums/images/graemlins/shocked.gifcross harbour master as fuel was being pumped out into the river.
Turned out the return pipes were cross which ment that fuel was taken out of one tank and pumped into the other and with one engine runnning over flowed one tank while empting then other.
So on a F33 with 2 tanks one in front of other they can be connected in either way.
All Sealines have a fuel transfer system, This allows you to run both engines of either tank, but normally running is each engine runs off its own tank, with the cross over valves closed, there is normally a diagram near the valves that shows you how to change things around if you need to.