5hp 4-stroke mercury with pull start only fuel problems

I am new on outboards, A friend and I bought the motor from a guy and he started it for us before we got it home. When we put it in the water, the motor wouldn't hardly start. When we would pull on the pull start gas would shoot out of the over flows. I got it to run for just a minute, and gas still poured out of the over flows. Got it home, took the carb apart, cleaned the entire system, put it back together, checked the spark plug and replaced, pumped the ball, will not start. I believe the gas was old to start with, But we replaced the gas before the carb cleaning. I even cleaned the fuel pump and the filter was clean. Any suggestions before we seek out a mechanic? We live in North Atlanta near the Chattahoochee, any known mechanics if no advice? There seems to be something small I am overlooking.