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2000 Merc 99 Idle Problem

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stormdad

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"Hello Group...I have a 2000 M

"Hello Group...I have a 2000 Merc 9.9 0T138308 that had sat for a while with fuel. Would start sputter and then stall. Bought a manual and started trouble shooting. Replaced all fuel hoses, inline filter, rebuilt the fuel pump and carb. Ran better but was surging at idle. Started trouble shooting ignition system. Everything checked out, but the ignition coil was not reading where it should be...So I replaced it with new. Engine still surging at idle speed. At higher rpm she runs great. Only when I back down @lower rpm does the rough idle begin again. Don't really want to buy parts that might not be causing the problem. And the manual says to test everything else before suspecting a faulty ECU/CDI.
Any and all suggestions would be greatly appreciated.

-Chris"
 
"Yes absolutely sounds like a

"Yes absolutely sounds like a low speed jet problem in the carb - missed a "cootie" there somewhere when you rebuilt her or chewed up/misaligned the carb base gasket when you tightened it back up.

Hmmm, didn't miss tightening the carb up nice and tight did ya - that would do it too...."
 
"JB & Graham, thanks for t

"JB & Graham, thanks for the speedy replies! I cleaned the carb with lotsa spray and then blew all the passages out with compressed air. According to the manual my carb does not come with an adjustable pilot screw. So I have no control over mixture. The carb rebuild kit came with what looks like a pilot screw (threaded stud with needle tip and o-ring). When I look into one of 5 tiny low speed passages I can see what looks like the tip of a needle partially blocking the passage-pin hole. There is a plug on the side of the carb that looks like it would cover the pilot screw...I'm hesitant to remove it...for one I dont have a replacement plug and two the manual says this model carb doesnt have a pilot screw??? Do you guys suggest popping the plug out and taking a look inside?

-Chris"
 
"I don't have first hand e

"I don't have first hand experience with it, but a little jb weld can fill it back in. A small drill bit on the plug and scribe to remove it."
 
"Graham, Yes this is a 4 strok

"Graham, Yes this is a 4 stroke.
JB, yes my manual diagram shows the jet as well, but says my serial range doesnt have it...but like I said I can see the tip of the jet partially blocking one of the passages.
Going to remove the plug and take a look, will devise a way to re-plug the hole. This is a link to my model carb http://www.crowleymarine.com/mercury_parts/3999/110.cfm

-Chris"
 
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