Chuck, when gas gets old from setting turpentine builds up and blocks the screen in your tank as well as the vent in your cap. When your tank gets empty see if you can put a little rubbing alchol on the screen to break up any turpentine built up on it. If not try and find some cleaner to pur in your tank to clean the screen. But be carefull and not use to much of it as it can be hard on your outboard motor. You maybe able to get something from a boat shop to put in it to do the job. Good luck and try to use some stable when putting it up next time if it is going to set for a while.