5 hp mercury 2002 flooding n dying n vapor locking

Hi , I recently a 2002 5 hp 2 stroke outboard , I bought it used and dont know much about it really , they told me it hadnt been fired up in 8 months or better when i got it . Took it to the river this weekend and on the way to my location i had to keep cracking the fuel cap open every 10 minutes , because it was pressuring up and killing the motor , granted it was 100 degrees , but i had the white screw almost all the way out , witch i would have thought would have remedy the problem , after we made the 6 mile trip , on the way back we made it 2 miles and it died and i couldnt revive it , choke in full throtle for an hour , i jerked the plug , it was soaked , turned the motor over 5 or 6 times to pump the gas out and reinstalled plug , full throttle , no choke , no fire , finally after trollin for 3 miles i turned the fuel switch off while starting it and finally got it to hit , an run the last mile ?????????? carb kit ? carb adjustment ? gas started pouring out of the thing at one point into the aluminum surround , no clue were from ! couldnt get i to fire up on the auxilliry fuel line for some reason had good flow to the disconnect on the motor ,
ANY ONE HAVE , ANY THOUGHTS ON MY SITUATION , ALSO LOOKN FOR A 10 - 20 HORSE THANKS FOR ANY WISDOM YOU CAN BESTOW UPON ME !!!