I have a 1970's model Johnson 2 cycle 40 hp outboard motor on the back of a 14.5 ft Fathom fishing boat. The engine has always started good and run well on plane...except after a time at open throttle, it will begin to gun and stop repeatedly. The last time that I had it out I had to pull the throttle back to idle, then bring it up to plane, where it would run a distance then bog down again. I started pumping the syphon bulb thinking it wasn't getting gas and it would run fine as long as I was keeping the ball pumped every so often. Then it finally bogged down and died. From this point it became hard to start, with or without choke, wouldn't throttle at all and finally wouldn't start and my battery ran down. I have checked the portable gas tank and everything in it is clear. I am looking for any help in this issue. Two other questions. I have been told that my gas tank should have a vent which should be open while running. Mine is an older metal model and there is no obvious vent. Also, I have been told that the syphon ball should be hard while running. Mine pumps up somewhat hard and then becomes easy to squeeze while running. Where should I start?
