Fuel filter / old gas

Fyi, I fired my boat up this weekend and it started up right away and ran fine right away. I made the mistake and put a container of gas that I thought was ok in the boat. It started up fine and ran fine until I stopped for lunch and tyen after an hour it idled like crap but I got it going and got back home. Since the tank was low , I went and got new gas filled it up , but when I went to start it would not idle or could I even fast Idle with gas. Fuel pump seemed to be working and it would fire just kept dieing. So It had been a while since I changed the fuel filter so, if we wanted to go see the fireworks I figured lets change it as I had a new one in the boat. Changed it, and captured about a cup of old fuel when removing, installed new one and the motor fired up like a champ and was back to normal. Im thinking I put a can of old gas in ( most likely) or the fuel filter needed changing.. ( maybe). Anyways just an FYI