metal fuel tanks

[route66_garage]

New question. Got my 9.9 evinrude running but one thing still puzzles me. This boat has 2 of the old style OMC steel 6 gallon fuel tanks. I do not see vents on them? Should the filler cap on this type of tank be left loose while motor is running so it will vent? I noticed that when the caps are tightly closed and in the sun for a while, and then you open one, fuel / air gushes out around the opening? Heat expansion I suppose? Should the caps be left cracked open at all times except during transportation? Thanks so much, dave

 

[Vic.S]

Re: metal fuel tanks

Some tanks have a vent which is opened automatically when the fuel line is attached. If not then should be fitted with vented cap.

 

[F_R]

Re: metal fuel tanks

See the two little pins that get pushed in when you attach the fuel hose? One of those pins is a fuel shut-off and the other is a vent. It is a one-way vent, meaning that it lets air in but won't let fuel slop out.