2001 Mercruiser 305 Rochester 2-barrel Vacuum leak?

[Boaty McBoatface]

I have a 2001 Caravelle with a Mercruiser 305. It has a Rochester 2GC carb. It has always had a problem coming off of idle, pulling up skiers, wakeboarders, etc. It just falls on its face. Once above 2000 RPM everything is fine and it runs great. I have narrowed the problem to the fact that the port side idle-air adjustment screw does not have any effect on idle mixture. The starboard idle screw works properly. If I spray more fuel into the port side, the idle instantly picks up.

First thing I tried was switching the idle-air mixture screws, no effect. The throttle plates seal up perfectly, and all passages in the carb are clear. I have sprayed carb cleaner around the whole top of the engine concentrating on the throttle shaft, carb gaskets, as well as all around the intake manifold. I currently have new intake manifold gaskets on order, thinking it may be pulling air internally from the center portion of the intake manifold in which case I would not be able to detect. I have been through the carb at least 3 or 4 times, looking for something I may have missed. If the intake manifold gaskets don't fix it I'm not sure what I'll do. Any thoughts?

 

[alldodge]

Howdy

You clean it 3 or 4 times yet one of the idle screws has no effect, but add mor fuel to the port side and it picks up. Tells be the idle circuit is still dirty.

As for the falling on its face, this is the accelerator pump issue in combination of not enough fuel on the port side. Most of the carbs to get then clean correctly takes a tank and they need to soak in a cleaning solution or ever better an ultrasonic tank. Note in the picks below the passages and accelerator pump circuit and check balls.

 

[jimmbo]

Another clue about the clogged idle circuit is it speeding up when you sprayed gas into it. Probably dirt/gum somewhere upstream of the mixture screw. Make sure gasket #61 is the correct one and all the holes that are needed are there

 

[Boaty McBoatface]

I have the carburetor apart on my bench right now. Tonight I'm going to fill the main well with carburetor cleaner and see if both the port and starboard wells fill at an even rate. I have checked the venturi cluster and everything is clear, so that leaves only the lower passages in the main carb body. Thanks for the tips, I'll take another look tonight... Just needed to make sure I'm not missing something blatantly obvious.

 

[jimmbo]

No Title

Compressed air, lots of it.

 

[Boaty McBoatface]

I finally figured it out. I started blowing air through the venturi cluster to try and figure out why fuel was moving on the starboard side and not the port side. It looks like some hack had previously pulled the idle bleeds and then pressed them back in. The port side idle air bleed was pressed in way too far actually blocking the idle pickup tube, essentially blocking off the fuel from the vacuum.... Now I just have to figure out how to get it pulled back without damaging the soft brass tube...

Thanks for the help on this.