Vetus m3 lift pump question

[themannsindorse]

I had persistent fuel starvation problems and so replaced all the pipes and new filters. Also cleaned out tank and fresh fuel. Result..motor still falters after a hours running THIS WAS THE CLUE however. It seems that the lift pump begins to fail once fuel in the tank had warmed up vie the return pipe. Why I am not sure but it did. My question is: On replacing the pump I found a 2mm shim between the pump flange and the Vetus m32 motor flange. What's its purpose.. anyone know? Is it Vetus's way of making pump fit other motors or by removing it, would it have made the little pokey thing from the motor pushed further into pump housing to make an old unit pump harder? Anyone know? Thanks. Peter