Yes, there certainly could be an issue like you stated. Fuel flow resistance increases when the length of the line increases. It is possible that the tank is stored too low in the boat, and that fuel pump isn’t powerful enough to pull it up. The fuel line could be pinched, or have an air leak somewhere.
Did this engine ever run correctly with this fuel pump set up? Is the fuel pump pulse line connected to the pressure nipple on the lower left hand side of the intake manifold? If so, modifications inside the manifold would have had to have been made so the pump receives both pressure and vacuum pulses. Does the intake manifold look like it has been removed before? And again, as others have pointed out, that line coming off the fuel pump looks as if it will get pinched when the engine cover is in place. So, perhaps the engine cover is pinching off the fuel supply or pulse line.
Did you pay a shop to make these modifications? If so, you might want to return it to them, repairs will probably be made free of charge. Like others have said, it would have been best to find the proper bypass cover with the fuel pump mount on it, and the pulse port drilled through. The set up on there is pretty hokey, but that does not mean it isn’t performing properly.
