TOPIC: Fuel Question

Ok, so I have the two new Moeller 6 gal plastic gas tanks with guage and ventable fill caps. I leave the vents screwed closed but one of the tanks seems to be creating a good vacuum and sucking in the top when it's used. I using it with the '59 Fat Fifty Should I be leaving the vent open on these? I was using the old Evinrude Cruise-a-day tanks before this. I don't recall a vent being on those. Well supposedly a drain by the guage, a corner screw but I think that only works if you remove that screw.

The engine also seems to be running rough now when ti's not at full throttle, like its not getting enough gas. Runs fine at full throttle. Float bowl looks fine on the pump. Don't know if something got into the carb and started blocking something. Thought maybe a bad wire but they all Ohm out the same and the rotor looks good on the magneto. Plugs are black, but even for all four, nothing significantly different between any of them.

Bob

The earlier single line OMC tanks had two pins that when you attaches the fuel line they would push in. One was to open the fuel, and the other opened the vent

Always open the vent as to keep from sucking in your tanks

Bob,you need to open the vent while the tank is being used so air can replace the fuel that's being pulled out. I've forgot a few times when switching to my plastic tank from the old omc metal tank on the lake.After I get under way again I look back to see the top of the tank sucked down .

Roger that, open the vents. Thanks guys!!!!!!!!!!!!!!!! We'll see how she runs tomorrow. Suppose to be 71 and clear, Woo Hoo, squeeze another day out! Going to check out the starter/solenoid issue too with the new little LED checker I got.

Bob

My dad bought several of those plastic tanks. (I'm not sure why. Our metal tanks were just fine) The OMC one has a vent in the cap that has to be unscrewed or the tank sucks in. The other ones were whatever brand Fleet/Farm had and have no visible vent, but never suck in and never leak.

From reading the posts her, got me to wondering. I have a old merc tank, probally 1969. And changed the fuel line fittings to hook up a non-merc engine. With the tank getting warm it does pressurise, so I'm sure it is not vented. I just rebuilt the carb because the motor was running lean. I have a merc male fitting at the tank, connected to a johnson fitting at the motor. Could this be creating a vaccuum at the tank causing it to run lean?

If it's a Mercury tank, it should have a knurled knob on top of the gas cap. That is the vent. Lacking that, then someone has replaced the cap. The mixture of Johnrude and Merc fittings has nothing to do with your issue.