I have a Mercury 8hp 4 stroke that is about 6 yrs old that doesn't like to keep running. Yesterday it first  ran 15 minutes no problem. But on the way in it will run about a 1/4 of a mile and shut off. The only way to get it started is take gas line off the motor, pump the bulb till it is hard, reinstall gas line. It will start 1st pull run another 1/4 mile and shut off. With line installed I can't get the bulb hard and I can pull for ever and it won't start. Seems like it is a fuel problem,  the fuel pump maybe? Anyone else have had this problem?  Thanks!!