vent opened or closed?

[Olias]

I hate to even ask such a stupid question but as I am brand new to outboards I really don't know. Question is, is the little vent/pressure cap button thingie on the gas can lid supposed to be opened or closed while running your motor? I have one of the newer plastic 3 gallon gas cells for reference. I assume it should be closed to allow pressure to build up in the tank which forces/feeds the gas through the line, right? The motor I'm running is in my signature if that info. is needed. Thanks

-B-

 

[colbyt]

Re: vent opened or closed?

If a dual line pressure tank the vent should be closed. It should be open on single line tanks which include 1960 motors which have been converted. The fuel pump pulls the gas in that case.

 

[Olias]

Re: vent opened or closed?

Thanks for your reply. Ok,that makes sense for my 60' Evinrude which has the dual line and older fuel pump, but my 94' merc has a single line going from the tank to the motor and I'm using the same style tank and I've been keeping the pressure cap closed on that gas tank as well and it runs great. In theory it shouldn't, right? Maybe I should try opening that up and see if it runs even better as it doesn't seem lke it's quite putting out 100%. I mean it runs very smooth but won't quite plane out my little 12' boat and I've checked for hub spin etc., and there isn't any. Hmmmm....I'll have to experiment. Thanks

-B-

 

[Home Cookin']

Re: vent opened or closed?

there are some tanks that the cap is vented when it's tight; some you vent by keeping them loose while driving; some have the small vent screw you open to run, close when not.

 

[colbyt]

Re: vent opened or closed?

Dual line systems did not ship with a fuel pump. The gas was pushed to the carb from the pressure of the exhaust port.

I don't see anyway you could use the same tank connecter on a modern motor. There may be an adapter that I am not aware of.