The two tanks on my 2005 40 Trawler are tied together with a piece of hose so that fuel can, in theory, be transferred from one tank to the other.
Problem is that one would need to be higher than the other to get it to flow over. If I'm transfering fuel it would be because the port tank, which feeds the genset and port motor, is much lower on fuel than the starboard tank which only feeds the stb motor. If there is more fuel on the stb side the boat lists to stb and the fuel won't flow into the port tank.
Also, the sender for the fuel gauge is on the stb tank, which sucks because it always has more fuel in it than the port side.