9.9 Yamaha kicker running a little rough.

My 2011 Yamaha 4 stroke 9.9 kicker doesn’t seem to run as smooth as usual. So far I’ve tightened the transom clamp screws, changed the spark plugs, and replaced the inline fuel strainer. The old plugs looked good. Used a generic in line fuel filter 40 mic that is bigger than OEM. So far no improvement. This week going to run it off a small portable tank with sea foam added to fuel instead of boat tank and hose. Anyone have ideas what it could be or what to try? I do run it at low rpms a lot but will run full bore a couple times a day. Never over heated and oil looks good.

Run some Yamaha Ring Free through it also. It’s basically Techron fuel system cleaner so you could use that instead of actual Ring Free.

You must be imagining things. From what I read on this forum there are never any issues with Yamaha outboards.

Might be imagining it. If I were catching more fish might not notice it.

isn’t that the truth. I’m pretty sure it must be an Etec painted up to look like a yamaha.

luckydave wrote:

You must be imagining things. From what I read on this forum there are never any issues with Yamaha outboards.

Are you running non-ethanol fuel?

Never run ethanol fuel for boat or lawn equipment. Have seen problems others have had though.
Thinking if fuel additive doesn’t impact problem then either carb or vacuum issue. Not a mechanic so will need professional help at that point.

9 years old, time for an actual carb cleaning not snake oil…

My Yamaha T8 was acting badly for over a year pulled the carb rebuilt it still running funky no matter what I did it would just not run right. Finally bought a new carb from overseas for a Yamaha 8 horse cost $68 actually has low and high adjustments and accelerator pump on it since they do not EPA over there. Bolted right up and Unbelievable how well this thing runs now it has never started and run so well, Touch the starter and it`s running hardly ever have to choke and not cold blooded like it was before..

Tom, who did you order the carb from. I think the carb repair kit for mine costs about that much.

There is a high speed and low speed jet on that carb. The low speed (Idle jet) can easily clog causing the idle or low speed rough running problem. Cut a wire off a new wire brush and poke it through the slow speed jet. Problem solved.

-J.