2003 Mercury 115 2 Stroke 4 cylinder outboard fuel problem.

[finish line 88]

Motor starts great, runs fine if I give it full throttle (cruises at 4400 rpms) but when it runs under 2000 RPM's it runs out of fuel. The primer ball goes soft so I must pump it to keep the engine running. I do have a spin on water separator filter in line. Any help would be great. Thanks

 

[ondarvr]

Air leak or failing fuel pump are the most likely causes.

​The primer bulb will always go soft when the motor is running.

 

[finish line 88]

Will the fuel pump pump less at low rpms than at higher rpms ? The primer ball is empty of fuel so in my thinking the fuel pump must be pumping fuel. I'll check for air leaks also. Thanks

 

[racerone]

Test run with a good portable tank and hose.