I have a 1996 Mercury 225 efi offshore that until recently was running flawlessly. The boat sat for about a year unused, tho I maintained a full fuel tank and ran it every couple of months. I topped off the tank with the 10% ethenol fuel and also put a container of the stabilizer made for the new gas. The motor was running fine the first time I took it out. However, now when I run it over 5000 rpms, it all of a sudden falls flat. If I pull back the throttle and punch it again, it will run for a minute then fall flat again. I have replaced all the fuel lines, both water/fuel seperators and found little debris if any. Initially i had a "cheap" primer ball that I noticed went flat when the engine died at full throttle, but replaced it with a "new better" primer ball and the motor still died, however the ball did not go flat. I tried to constantly pump the ball as I ran the boat at full throttle, but it still died, and the ball remained hard and full of fuel. If you have any suggestions for me I would greatly appreciate it. 
