Its a 2001 mercruiser 4.3 v6, carburated. Had not run in maybe 1 1/2 years. I changed the oil and filter, and fuel filter/water separator, used earmuffs and a hose for cooling, and after some cranking and pumping the throttle, it started, ran for 5 minutes or so, and then it died. I could not get it to start again. Poured a little gas into the carb, and it would start, but not run. I tested the fuel pump, and oil pressure switch, had power to the pump, and when I direct wired the pump, it would not run. I ordered a pump, installed it, and verified that it would run (can hear it run while cranking, and then for a few seconds until the oil pressure drops on the gauge). Again, it would pop, run for a couple of seconds, backfire thru the carb, and die. I went ahead and replaced the plugs, distributor cap, and rotor. I am still having the same issue. I can hear the pump run, and I can pump the throttle, and it will start, but immediately dies, and it back fires thru the carb. Has me stumped. I can understand the fuel pump going bad, but what else? As I said, it was running prior to the pump going bad. I checked the fuel filter at the carb, and its clean. Could plugged jets from sitting with old gas cause this? The gas in the boat is probably 1 to 1 1/2 years old, but like I said, it did start and run for 5 minutes or so, until the fuel pump went bad. I did add some octane booster and a can of Seafoam to the tank. I am thinking of pulling the sending unit off the tank to look in it, in case its a mess in there. Any ideas or suggestions? I have owned the boat since new, and it has always been trouble free and reliable. Hour meter shows 419 hours.