From Holley Marine Performance Products
Marine carburetors have certain modifications that make them uniquely  adaptable and legal for marine usage. "Legal" meaning that it has the ability to pass the U.S. Coast Guard test for marine carburetors. Folks, I'm not talking about Paris Island here, either. The main qualification that a marine carburetor must meet (as set down by the U.S. Coast Guard) is that if the carburetor should "flood" only .5cc of fuel is allowed to escape in a period of 30 seconds. There's also a "backfire" test which confirms the ability of carburetor/flame arrestor combination
to contain the backfire. For this reason a gasket is not used between the carburetor airhorn flange and the flame arrestor. It's possible that this gasket could become saturated with fuel (if the carburetor should flood) and become a potential fire source as a result.

The primary areas of a carburetor that require some sort of modification to meet these requirements include the fuel bowl vent tubes and throttle shafts. The vent tubes of a marine carburetor are bent inwards so that the tube looks like an inverted "J". These tubes oftentimes are referred to as "J" tubes, as a result. The reason for bending the tubes inward is that if flooding should occur, the fuel that would normally come out of the fuel bowl vent tube is rerouted back into the carburetor.

Throttle shafts also get special machining attention. Shafts are "grooved" and "slabbed" to prevent fuel from exiting out the throttle shaft if flooding should occur. When a carburetor floods fuel will end up "puddling" on the throttle plates. A non-marine carburetor will allow this fuel to seep out of the throttle shaft ends and onto the manifold. This is not allowed on a marine carburetor because normally the engine is situated in an enclosed bilge where potentially deadly gasoline fuel fumes can accumulate. Throttle shafts that are "grooved" and "slabbed" channel the flooded fuel safely down into the intake manifold. With no raw fuel allowed to puddle on the manifold outside the carburetor, there is no chance of deadly fuel fumes to accumulate in the bilge and no chance of explosion or fire. For these reasons an automotive carburetor should NEVER be used in a marine application. 

Carburetor Descriptions Performance Show Carburetors 
Holley Performance Show marine carburetors are available as four barrels in either square (Model 4010) or spread bore (Model 4011) flanges and also as a two barrel (Model 2010) with the 2300 flange. These are universal marine carburetors that can replace existing Rochester Quadra-Jet, Rochester 2GC, Carter AFB/AVS and Holley two and four barrel carburetors that were original equipment on various marine engines. These carburetors come equipped with an electric choke and the four barrel models have dual feed fuel bowls. The 5" airhorn of these carburetors will allow you to use the existing flame arrestor of the old carburetor. Some minor fuel line routing will be required to accommodate the dual feed fuel line. 

The Holley model 2010, 4010 and 4011 marine carburetors all utilize annular boosters. This unique design provides for a relatively stronger vacuum signal and provides a very smooth and linear transition to the main circuit with superior fuel atomization. Throttle response is "Right Now" (great for pulling skiers up) and, once on plane, fuel economy is enhanced. An added benefit of these carburetors' design is the ability to easily "best Jet" them without removing the carburetor from the manifold. Simply remove the top airhorn cover casting. The fuel level is below the casting line so there is no danger of fuel spillage. The carburetor main jets can be accessed on the floor of the respective fuel bowls. 

Standard Holley parts are used in these carburetors so jets, power valves, vacuum secondary diaphragms and springs, etc. are no problem. Special marine carburetor rebuild kits are available for these, and all Holley marine carburetors. This catalog has the complete listing of carburetors and kits. Also, special Holley chrome dual feed marine fuel lines are required for the Models 4010 and 4011 carburetors. These are listed with the respective carburetors in this marine section. 

Performance Carburetors  Square Flange 4 Barrel 
Holley marine Performance four barrel carburetors are available in both the model 4150 and 4160 styles. Sporting universal marine calibrations, these carburetors are available in CFMs ranging from 600 to 850. Depending on carburetor there's a choice of mechanical and vacuum secondaries, manual and electric chokes and single or dual feed fuel bowls. Holley marine carburetors use standard Holley parts and special marine carburetor rebuild kits are available. These carburetors could be used to replace existing Carter AFB/AVS and Holley original equipment carburetors. They're also a good choice for upgrading, say when changing over from a two barrel to a four barrel fuel system. 

Performance Carburetor 4500 DOMINATOR HP 
The 4500 DOMINATOR HP marine carburetor is available only with a racing calibration. IT'S RECOMMENDED ONLY FOR ALL-OUT RACING TYPE ENGINES. The 4500 DOMINATOR HP uses a special flange that requires either a special manifold or use of an adapter, like Holley P/N 17-9. The 7" air horn flange also requires use of a special flame arrestor to accommodate this extra large size. This carburetor is unique in other ways since it does not incorporate a choke nor does it have provision for one. The bottom line is that this is not your ordinary replacement carburetor for your family ski boat! 

Replacement Carburetors 2300 Flange and Square Flange 
Holley marine replacement carburetors are designed as exact replacements for Holley carburetors that were original equipment on various late model Ford, OMC and Volvo marine engines. These carburetors are literally bolt-on replacements for the applications listed. Throttle, choke and fuel connections should hook right up without any problem. Holley makes it easy to regain original equipment response and power with new marine replacement carburetors. 

Identifying Carter AFB Carburetor Bolt Patterns 
The Carter AFB carburetor was used on many marine installations over the years. The bolt pattern of the "early" AFBs differ from the later models. When replacing an AFB carburetor with a new Holley marine replacement carburetor it's important to know what you've got. The illustrations, at left, will clarify the two different bolt patterns used on the Carter AFB carburetor.

Early Carter AFB Bolt Pattern  When replacing with a Holley model 4010 carburetor the following is required: P/N 17-7 adapter P/N 717-5 throttle cable bracket (or P/N 17-23 spacer) placed between the carburetor and adapter to prevent vacuum leaks.     Late AFB Bolt Pattern  This pattern is exactly the same as the Holley model 4010, square bore carburetor. No special adapter is required for this installation.

Holley Marine Carbs