The deflector vanes impart a swirling motion to the air entering the air cleaner and centrifuge the dust particles against
the walls of the tubes. The dust particles are then carried to the dust bin at the bottom of the cleaner by approximately
10% bleed-off air and are finally discharged into the atmosphere. The cleaner panel is fully effective at either high or low
The remainder of the air in the cleaner reverses direction and spirals back along the discharge tubes again centrifuging
the air. The filtered air then reverses direction again and enters the replaceable filter element through the center portion
of the discharge tubes. The air is filtered once more as it passes through the pleats of the impregnated paper element
before leaving the outlet port of the cleaner housing.
The cleaner panel tends to be self-cleaning. However, it should be inspected and any accumulated foreign material
removed during the periodic replacement of the impregnated paper filter element. Overloading of the paper element will
not cause dirt particles to by-pass the filter and enter the engine, but will result in starving the engine for air.
The filter element should be replaced, as operating conditions warrant, as follows:
1. Loosen the wing nuts on the fasteners and swing the retaining bolts away from the cleaner panel.
2. Lift the cleaner panel away from the housing and inspect it. Clean out any accumulated foreign material.
3. Withdraw the paper filter element and discard it.
4. Install a new filter element.
5. Install the cleaner panel aid secure it in place with the fasteners.
The air silencer, used on some marine engines, is bolted to the intake side of the blower housing. The silencer has a
perforated steel partition welded in place parallel with the outside faces, enclosing flame-proof, felted cotton waste which
serves as a silencer for air entering the blower.
While no servicing is required on the air silencer proper, it may be removed when necessary to replace the air inlet
screen. This screen is used to filter out any large foreign particles which might seriously damage the blower assembly.
Air Box Drains
During normal engine operation, water vapor from the air charge, as well as a slight amount of fuel and lubricating oil
fumes, condenses and settles on the bottom of the air box. This condensation is removed by the air box pressure
through air box drain tubes mounted on the side of the cylinder block.
The air box drains must be open at all times. With the engine running, a periodic check is recommended for air flow
from the air box drain tubes. Liquid accumulation on the bottom of the air box indicates a drain tube may be plugged.
Such accumulations can be seen by removing the cylinder block air box cover(s) and should be wiped out with rags or
blown out with compressed air. Then remove the drain tubes and connectors from the cylinder block and clean them
Some engines are equipped with an air box drain check valve. Refer to the Lubrication and Preventive
Maintenance section of this manual for service instructions.
Harmful vapors which may form within the engine are removed from the crankcase, gear train and valve compartment by
a continuous, pressurized ventilation system.
A slight pressure is maintained within the engine crankcase by the seepage of a small amount of air from the airbox past
the piston rings. This air sweeps up through the engine and is drawn off through a crankcase breather.
In-line engines are equipped with a breather assembly which is mounted on the rocker cover or the flywheel housing.
The 6V engines incorporate a breather assembly mounted inside of the upper engine front cover.
The wire mesh pad (element) in the breather assemblies should be cleaned if excessive crankcase pressure is observed.
If it is necessary to clean the element, remove the breather housing from the flywheel housing (In-line engines) and the
upper engine front cover (6V engines). Wash the element in fuel oil and dry it with compressed air. Reinstall the
element and the breather assembly.