1986 Mercury 115HP inline 6 fuel issue

[Jcnehalem]

I have started to have some weird symptoms with my 115HP Merc. The other day the motor started just fine but when giving the motor throttle to get on a plane it started to lose power. After trying a few times I thought maybe it was starving for fuel so I reached back and squeeze the primer bulb. The motor came to life with full power. That day I had to keep squeezing the primer if I wanted to stay on a plane. I thought maybe it was my primer leaking air because when I squeezed it real hard some fuel would come out of the end. I put new hose clamps on the primer and now there is no fuel coming out when I squeeze it real hard. The next time I ran it I had no problems so I thought that fixed the problem. But then the next time I took it out it wouldn't start. If I pushed in on the key to choke it would almost start. After 30 minutes of screwing around I squeezed the primer really hard and then it fired right up and ran fine the rest of the day.

My Primer was new last spring so I don't think it has any problems. When I pump the primer it gets really hard to where I can't really squeeze anymore. I am wonder if these symptoms could be a fuel pump issue. I haven't tried changing my fuel separator because fuel seems to get into the primer fine.

Anybody have some thoughts?

John

 

[swamp-fox]

Re: 1986 Mercury 115HP inline 6 fuel issue

If it runs better when you squeeze the bulb then it's definitly a fuel problem. I would start with the water separator, change the filter. If you can bypass it (and know you don't have any water in the tank), run it without it and see if that helps. You said you fixed the clamps so that' s good, but make sure it isn't leaking anywhere else. If it's leaking gas then it's sucking air when you are running.
Then it could be a few things. A little piece of trash can hang up then when you kill the engine it might allow gas to pass, hence somethimes it runs fine.

Make sure conections are sealed, then fuel filter clean, could be primer bulb. After that I would say fuel pump.
Just because bulb was replace last spring doesn't really mean anything. Ethenol in gas can eat fuel lines and things like that up in a month.
Learned that the hard way...