Air in fuel line question.

I have a 2001 Mercury XR6 150 with oil injection and carbs. It runs erratic at times and I've noticed that the primer bulb won't get firm no matter how many times I pump it and air is entering the line somewhere. I can see it when it enters the fuel filter. I've replaced the primer bulb and the gas line from the primer bulb to the fuel filter on the engine. This did not solve the problem. Is there a way to check if it is the line from the tank to the primer bulb without just replacing the line itself? Could air be entering in from the oil injector line somewhere? I have a problem with the oil warning buzzer going off in the past and everynow and then I'll unscrew the cap on the engine oil reservoir and it fills up. This has been happening since I bought it used in July 08. It has been running fine untill a week ago. Thats when I noticed air in the line. Any suggestions would be appreciated.

Re: Air in fuel line question.

Check to "O" rings in the boat oil tank connection. Maybe put a little Vaseline on them, it cause the rings to swell a little. A vacuum leak is hard to detect because it only shows air once it has entered the line.

Re: Air in fuel line question.

Thanks, I'll give the vasaline a try. I was told that a faulty fuel pump (Diaphram)would cause the bulb not to get hard when you pumped it. Does that make sense?