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If it looks like a duck and quacks like a duck, it must be a duck.
Right? Well, maybe. Carburetors are carburetors, but only marine
carburetors should be used on boats. It's true that marine carburetors started life
as regular automotive carburetors but then each took divergent paths.
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 carburetors/flame arrestor combination to contain the
backfire. For this reason a gasket is not used between the carburetor air horn 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 DESCRIPTION
Performance Carburetor
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 CFM's 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.
MARINE CARBURETOR DESCRIPTION
Replacement Carburetor
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 replacement
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.
MARINE CARBURETOR DESCRIPTION
Replacement Carburetor
4500 Dominator
The 4500 Dominator marine carburetor is available only with a racing calibration.
It's recommended only for all-out racing type engines. The 4500 Dominator uses a
special flange that requires either a special manifold or use adapter, like Holley Part Number
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!
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