Question

I have a 1994 Starcraft with a 4.3LX V6 Alpha one. My problem is fuel related. The problem started on a fishing trip. The boat had started fine for 8 years. In the middle of the trip it I replaced the fuel pump when I got home but the problem persisted. The next season I tried pulling the fuel line at the throttle body and, using a syringe, injecting gas down the fuel line towards the pump. I was able to start the boat and use it all day, restarting as necessary. The following day I had to repeat the "gas down the fuel line" procedure to get it started. This year, once again it wouldn't start. I pulled the fuel line from that runs from the tank to the filter. It was dry. I replace the line, sealed the threads on the fittings. I started the boat two days ago with the fuel down the line method. Let it sit for two days and it wouldn't start until I primed the fuel system again. It seems that fuel is draining down the system back into the tank creating a vapor lock of sorts. What to do?