The Holley 4010 and 4011 are 2-piece aluminum carburetors used mainly on marine applications and available in the aftermarket since the 1988. The 4010 uses a Holley squarebore flange (5.16 X 4.625 inch bolt centers) and the 4011 uses a spreadbore flange (4.25 X 5.62 inch bolt centers). Both series were available in either vacuum secondary, or mechanical secondary (double pumper) versions.
These carburetors use the same type power valves, accelerator pump actuating arm, linkage, cam, pump diaphragm, needle and seat, secondary vacuum diaphragm, secondary diaphragm springs and chokes as the original Holley 4150/4160 carburetors.
Carburetor numbers are stamped on the front of the choke tower. How to find Holley carburetor list numbers