Johnson 15 Hp 4-stroke Running Rough WOT

[walleyekid85]

Idles fine, but when you give it gas starts to run rough. Does it both in nuetral and in gear. Does it sooner when in gear. Any ideas? Sparkplugs?
Is there any carb? adjustment? Do I have to drill out a brass cap?
Motor is a 2004

[jimmythegreek]

pull it out and give it a good cleaning, look on youtube they are SO easy dont even worry. I just did my 6hp kicker it runs better than when it was new, no BS. I drilled out the cap and adjusted the fuel/idle mix and its so crisp, its BS they have it covered, never ran better, I didnt replace the gaskets or jets, just be careful getting htem off, took 20 mins tops, Im doing it every year from now on in the spring

[Water Fowl]

Walleyekid85,
Has this motor just starting doing this or has it always ran this way? Or is this a new motor to you? The 2003/2004 small 4-stroke Johnsons had a known issue with running too lean at idle. Search "2003 johnson 9.9 4 stroke problems" and you will see what I found when we had a similar problem with our 9.9 Johnson back then. Motor hasn't missed a beat since doing modification suggested in the thread. Not saying it is the problem but there was a known issues with them.

Water Fowl

[walleyekid85]

this is a new motor to me. I started drilling the brass cap but stopped since I wasn't for sure if I was drilling the right thing. The Cap seemed to be pretty thick. Anyone have any photos?
Thanks