When i bought my boat it came without a fuel pump. I put a stock fuel pump off of another ford engine on it. I think it came off of a 302 or something like that. The boat runs fine and idle and without load but as soon as there is a load on it (in the water) and you step on it it revs up fine and then boggs down after a couple of seconds, If you return it to idle and then rev it again after a couple of seconds, its back to being perfect. Could this be the Fuel pump not filling the bowls up quickly enough?