Need HELP with MERCARB won't throttle down below 2500 RPM after rebuild

[jimmoe]

My '89 3.0 alpha 1 with a 2bl mercarb wasn't running right after sitting for a summer, It wouldn't run smooth or idle so I rebuilt the carb, it was very dirty and one of the throttle plates was badly bent. I had it cleaned in a sonic cleaner, blew out all the passages, had to fine wire ream one venturi bore and got the plate back in shape so it looks and fits just like the other one. I used the spring style float needle.
Now it will start and run but only at 2500 rpm's or more.
I've pulled it several times, re-checked the whole procedure, triple checked the float settings, backed the new idle "needle" screw out 1_1/2, set the choke unloader setting to 5/64, and backed the idle stop screw totally out. I noticed the throttle plates do not completely close off the openings...I can see just a sliver of a gap thru them when I held 'em up to the light and thought that was normal.
It starts pretty easy with a few throttle squirts but will not keep running unless I throttle it up to at least 2500. I can see it feeding fuel at that speed but not any lower.
It's like there is no fuel at all coming thru the idle circuit?
I don't know how to check that or what to do next......please help!

 

[Boat Doctor1]

is the fast idle cam on backwards?? look to see whats holding the butterflys open!!

 

[alldodge]

If the throttle cable is disconnected from the carb the idle screw is not touching the throttle cam, and you can hold it more closed and has near no effect, then I would replace the carb

 

[jimmoe]

so..... the idle cam was correct, I tweeked the blades a little and they fit tight now, everything was happening exactly like you said Dodge and no improvement.
However, when I saw the price tag on a new mercarb, I decided to go thru it one more time. I found a document on line with a good explanation of carburetor circuitry and gleaned enough to know what to look for. I tore it down again and did find a gray slime/sludge blocking the brass idle tubes on the venturi. I figured it was ethanol having separated from the gas after sitting in the tank for a year or more. I cleared it out.....drained and cleaned the tank as best I could, pumped a gallon of clean premium gas using the fuel pump till it came out clean. She started up, ran and idled down nicely ! Back on the water !

 

[alldodge]

Glad to hear, and thanks for coming back and closing the thread. Have a great boating day