Holley carb on Volvo Penta 3.0 GSM-A will not idle

[rrc0]

Just rebuilt a Holley marine carb series 2300 serial number 80316-3.
It is original to a 2001 Model year Volvo Penta stern drive with a 3.0 liter GSM-A engine. I have no idle after carb rebuild. Even with the throttle idle speed screw all the way out, the engine won't slow to less than 1000 rpm. I had the same problem before the rebuild. In addition, the idle mixture screws seem to have little effect. Searched for vacuum leak with propane enrichment, but found no leaks. The ignition timing is correct and engine pulling good vacuum. What am I missing?

 

[Scott06]

Did you adjust the throttle linkage to close all the way or disconnect it ? At 1000 rpm youll be off the idle circut and into the transition circuit so the idle mix adjustment wont matter

not sure if these holleys have a idle air bleed that bypasses air around the throttle blades ? Did you verify the throttle blades are closing fully and not hung up

 

[Lou C]

go on to Holley.com there's a lot of information there.
it sounds like you have a blockage in your idle circuit either in the fuel supply or the air bleeds and have to go at it and clean it better. When you pull off the float bowl you really have to clean all the passages in the metering plate & throttle body and the air bleeds that are in the air horn area. When rebuilding carbs cleaning is 90% of the work.

 

[rrc0]

ScottO6, I disconnected the throttle cable and operated the throttle by hand. The idle speed screw is all the way counterclockwise (to slow the idle). The throttle blades are fully closed. Throttle plates were reassembled correctly and are closing fully.
Lou C, spent significant time cleaning the throttle body and metering plate. Blew out all passages and compressed air moved freely thru passages. If I forcefully pull back on the throttle linkage, the rpms will slow slightly, but that certainly isn't the way that throttle shaft return spring and linkage should work.
No vacuum leaks found.