I have a 1985 35hp Mercury outboard on a small fishing boat. Most of the time the motor runs perfect. Occasionally I will be on the water running and the motor will die. You can pump the ball but it will never get completely filled with gas. To keep the motor going I have to keep pumping on the ball while running. I have rebuilt the carb, replaced the hose, tried two gas tanks,replaced the fuel pump diaphram and still the same thing. Again, I can go out for days or weeks and it will not happen again. It's almost as if the ball gets an air lock in it. Any ideas on how this happens and how to prevent it?
About the only thing ya missed was the fuel pump but I can't understand why its failure would be intermittent,. They usually work or they don't. The fuel pump works from pressure pulses from the crankcase and you may have something interrupting those like a leak or stopped up orfice. I'd check around there first and then maybe rebuild the fuel pump.c/6Hooty
Mornin' rverano,Hooty probably has you goin in the right direction but I couldn't help but get hung-up on your comment about the bulb. These bulbs can be squirely on occasion. If the fuel pump doesn't get you fixed, try replacing the bulb.You can pick one up at Walmart for a couple of bucks.Good LuckHAVE FUN!
Try putting about 10 inches of clear hose between the primer bulb and the fuel pump and look for any air bubbles. If you see air bubbles, then you have a vacume leak somewhere. Pick up in gas tank,hose conection, ect.
I almost forgot, do not buy one of those cheap primer bulbs from wal-mart. Spend the extra few dollars and but one from your local marine dealer. Those ones from wal-mart are plastic and will fail after a few months.