I have an 18 hp 1968 evinrude a great running motor that I use for trolling, it trolls great will run all day , when I run in at full throttle the engine RPMs decrease and the engine will stop, I can run at 3/4 no problem. when the engine stops the fuel lines are empty, squeeze the bulb and it fires right up only to die again. I have changed tanks - left the cap loose richened the carb. nothing helps, any ideas. Ken 