Engine Systems
they have a permanent set, a new impeller should be
Raw Water Pump
used. If the impeller area which rides on the wear
plate is damaged, the impeller should be replaced.
A positive displacement raw water pump driven by a
coupling from a camshaft circulates raw water through
5. Insert two wires (each with a hook at one end)
the heat exchanger to lower the temperature of the
between the housing and seal, with the hooks over the
engine coolant.
edge of the carbon seal. Then pull the seal assembly
from the shaft.
The impeller (Fig. 20) is self-lubricated by the water
pumped and should be primed before starting the
6. The seal seat and gasket may be removed in the
engine.
same manner.
Rubber spline plugs have been inserted between the
7. Remove the cam bolt and cam.
end of the drive shaft and cover to reduce the
possibility of foreign material working into the splines
8. Remove the wear plate and check it for wear and
and causing wear.
burrs. If the plate is worn or burred, it may be
reversed.
Note that the end cover is marked to show the outlet
port for RH rotation and the outlet port for LH
9. Install the wear plate. There is a dowel in the pump
rotation. Follow these markings when installing the
body, and the wear plate is notched to ensure correct
raw water pump to assure proper direction of flow.
installation.
Also, when installing the inlet elbow or outlet elbow,
be sure to use two flat washers on the bolt being
10. Hold the cam in position and install the cam bolt.
installed in the blind hole in the pump housing
11. If the seal seat and gasket are removed, place the
A rotary type seal assembly prevents any leakage
gasket and seal seat over the shaft and press them into
along the shaft.
position in the seal cavity.
A raw water pump seal failure is readily noticeable by
12. Place the seal ring securely in the ferrule and, with
the leakage of water from the openings in the pump
the carbon seal and washer correctly positioned
housing. These openings, which are located between
against the ferrule, slide the ferrule over the shaft and
the pump mounting flange and the inlet and outlet
against the seal seat. Be sure the seal ring is correctly
ports, must remain open at all times.
contained within the ferrule so that it grips the shaft.
It is possible to replace seal parts and the impeller
13. Install the flat washer and then the marcel washer.
without removing the pump from the engine.
14. Compress the impeller blades to clear the offset
Use care to prevent scratching the lapped surface of
cam and press the impeller on the splined shaft. The
the seal seat or that portion of the shaft which the seal
impeller blades must be correctly positioned to follow
contacts.
the direction of rotation.
The raw water pump seal parts and impeller may be
15. Turn the engine over a few revolutions to position
removed and replaced as follows:
the impeller blades properly. Install the spline plugs.
1. Remove the cover screws and lift the cover and
16. Use a new gasket and install the cover on the
gasket from the housing (Fig. 20). Note the position
housing.
of the impeller blades to facilitate reassembly.
The Jabsco raw water pump is equipped with a
2. Grasp a blade at each side of the impeller with
synthetic rubber impeller. Since synthetic rubber loses
pliers and pull the impeller from the shaft. The spline
its elasticity at low temperatures, impellers made of
plugs will come out with the impeller.
natural rubber should be installed when it is necessary
to pump raw water that has a temperature below 40 F
3. Remove the spline plugs by pushing a screw driver
(4 C).
through the impeller from the opposite end.
The synthetic rubber impeller must be used when the
CAUTION: If the impeller is reusable, care
pump operates with water over 40 F (4 C).
should be exercised to prevent damage to the
splined surfaces.
4. Inspect the bond between the neoprene and the
metal of the impeller. Check the impeller blades. If
Page 30
