Mercury 4hp 4stroke running too rich at idle

[TimFromLI]

My mercury starts right up -without the choke when cold. Then when warm, I need to keep the RPMs high to keep it idling. It makes coming into the dinghy dock very exciting since I have to come in at fast idle. Is there anyway to fix that. Is there a way to adjust it or should I remove the carb and try cleaning it.

 

[kloudie1]

First, check that when the choke is pushed in, the choke plate in the carburetor is actually fully open. The design of the choke cable holder/clamp on that engine is kinda shaky and may not push the choke off. If that is not the problem, the next thing would be the float needle leaking and needing a cleaning or replacement. I don’t recall any mixture adjustment on that carb.

 

[kloudie1]

On the other hand, the usual problem is too lean at idle, requiring more throttle to start pulling fuel from the medium/high speed circuit in the carb. If too lean, then a thorough carb cleaning is in order.

 

[TimFromLI]

Thanks, it's definitely too rich. it won't start with the choke on. The problem started after I put a new carb on it. I'll check the choke plate and bowl. maybe I'll try the old carb, again. I only changed it because the engine wouldn't start. It turned out it was the plug not the carb so the old carb is probably still good.