Before you install that replacement part, run the engine & make sure that exhaust fumes are not coming from the connection hole in the intake?  If that happens to be the case, (hopefully not) it would indicate that the tube in the intake "crossover" is also rusted out & needs replacement. Maybe Kultutz can provide a part # for that too..  Up here in west coast Canada, some time back, I could not find a listing for that part.. I made my own, but that's another story..       


Paul

THERMOSTATIC CHOKE CONTROL TUBE - INLET

1956 MERC 312 CARTER

ECK 9820-C

- https://nospartsltd.com/product/eck9820c/

____________________________

On some 312's (maybe all?), there is an item referred to as Automatic Choke Vent Tube.  It has a special press-in 90° elbow fitting connected to the manifold just below the carburetor (mine is a Carter--don't know if that matters).  From the elbow, the tube travels up to where it is inserted in a grommet in the carburetor body.
It can be seen behind the throttle linkage in the highlighted portion of this photo.

Mine is damaged, but I have not found a parts place or mechanic who is even familiar with this.  Does anyone have a suggestion on where to find or if this part is even needed?  Maybe an idea on how I can fabricate one?  If it helps, this engine is from a 1956 Mercury.