Carb fouling at low speed / Idle?

[Robtile]

I saw what appeared to be a well-maintained 2003 Evinrude 9.8 HP 4 stroke today (pull start) at my local marina. The marina told me that the history of the engine was that they had fouling problems with it. It was used as a kicker and when it would run at low speeds for long periods, the carb would foul. She said they drilled it out, and even changed the complete carb and could not mitigate the problem when used in a low-idle capacity for long periods (why a kicker would be "low idling" I don't know).

Nonetheless, she said if I were to buy it and use it as a fishing motor on my 14' boat she sell it in good conscience, but should I want to use it as a kicker on my larger boat, she would not recommend selling it. She also said that it was actually a Johnson 4-stroke, painted and branded to look like an Evinrude to match the original owners main engine. Also weird, but I had a 55 HP 4 stroke Johnson that I loved so that doesn't bother me, albeit it may be relevant to diagnosing a known problem with the carburetor problem so I thought I'd mention it. I need to get a closer look at it to confirm that.

The obvious thing to look at (to me) would be problems with ethanol fuel that might be remedied with higher octane fuel and some Sea Foam. But that seems so obvious that I can't imagine the mechanics didn't consider that. I appreciate the marina's honesty and they do an excellent job of maintenance on my 90 HP e-Tec, so I know their mechanics aren't incompetent.

Anyone heard of such a thing on a newer motor or have similar experiences?

 

[jakedaawg]

Re: Carb fouling at low speed / Idle?

I wonder if the motor, while being used as a kicker, was lugged too much and/or improper mounting. It seems to me that if it sat way to deep in the h2o that it might not exhaust well causing carbon fouling of the plugs. Was it the carb that was gumming up or were the plugs repeatedly fouling?

 

[steelespike]

Re: Carb fouling at low speed / Idle?

Thats interesting,I don't find any small Evinrude motors listed in the NADA price guide 2003.
I'm pretty sure regardless of the brand they are both Suzuki built.
While I salute the dealer for their honesty; I wouldn't be buying a a motor with a problematic history.
You might want to establish brand and look up availability of simple things like impellers,props, fuel system and ignition parts.

 

[Robtile]

Re: Carb fouling at low speed / Idle?

Yes, thanks, Gentleman. As I noted, it's actually a 2003 Johnson 9.9 HP (not 9.8 HP), painted and branded as an Evinrude. I did find a post after this one noting that the 9.9 HP 2003 4-stroke Johnson's were noted for their inability to low idle w/o difficulty (which was subsequently fixed by a 2005 redesign of the motor). The fix for low idle difficulty (according to another older post on this site) is to drill out the plug to access the idle adjustment and then drill a 1/16" hole in throttle plate. That will allow them to be idled down and still get the amount of oxygen required. Whether this was the problem with this one I can't say. I went back and looked at the motor today and lunch and the plug was drilled out to access the idle adjustment, but I'm guessing they never drilled the hole in the throttle plate.

I am guessing the marina was referring to plug fouling (and not carburetor fouling). Sitting too low in the water is something I never considered either. Thanks for your help. They'd let it go for 1/2 of a new one, and it appears to be in excellent shape, but even at 1/2 a new one, it's still a lot of money if it's something I can't manage!