1999 15 HP Evinrude Rough Idle Issues

[leenover]

I have a 1999 15HP Evinrude motor that has a tough time idling while trolling. It will start and run fine and all RPMS except low idle. Iit will idle for a couple of minutes, cough thru the carbs and either catch and run high RPM briefly, or stall all together. Simple pull of the chord gets it started again but might do it again immediately or after 5 - 10 minutes. Their is no pattern when it will sneeze. Took carb apart to clean and it was spotless. New tank and hose, plugs look clean, gas is new. Ran Seafoam thru it, still no luck. Taking the carb apart did help it a bit, but still coughs thru carb. What should I do next? It will run 1/8, 1/4, 1/2, 3/4 and full throttle for hours, but idle is sporadic. Idle mixture screw set at 1 1/2 turns out. 1 turn out and 2 turns out made no difference.

 

[racerone]

2 stroke or 4 stroke ??-----Model # always helps.

 

[leenover]

Sorry. It's a 4 stroke. Model # E15R4EEB. More noticeable first start of the day. If you leave it sit for 5 or so minutes, it is hard to start, usually requires quarter throttle to get it started.

 

[racerone]

Check the valve clearance !------Some of these motors have a problem with worn rockers which results in problems with opening / timing of the valves.

 

[leenover]

Turning the idle adjuster in 1 turn helped some as it doesn't cough. Will go out trolling and see it how runs.

 

[leenover]

Update. Drained regular gas and replaced with Premium. Idles and trolls fine. Trolled for 45 minutes without a hiccup. I think I forgot to install the Diaphragm Plunger in the accelerator pump (pic below, please verify that is what it is). Will that affect much? I found it on the floor after putting everything together.