primer bulb or fuel pump

[fishin0001]

96 Mercury 40hp 4cylinder,My last post on this issue was trying to get the carb mixture screw just right so I got it good enough to go fishing and forgot about it, being happy with no idle and choking carb to get it to speed.yesterday I had it running and noticed when I very lightly kept squeezing the primer bulb it idled even under load.how much pressure should the fuel pump put out and Im going to buy a new primer bulb but is there a sure fire way of testing primer bulb since I have to travel a ways to get one....just my thoughts
Thanks

 

[GA_Boater]

The sure fire way of testing the primer bulb is rebuilding your fuel pump. The bulb has nothing to do keeping the motor running, it only fills the float bowls for initial starting. Squeezing the bulb to keep it idling shows the bulb is fine. it's the fuel pump.

What happens is the diaphragm gets stretched and at low RPMs the pump can't supply the volume or pressure. As RPMS increase, the pulses driving the pump overcomes the stretch.

 

[fishin0001]

Thanks ...going to order the kit