Chrysler 6, 7.5, 180 Sailor Outboard Motors Service Manual, OB 3330, Page 114Get this manual
Subsection
_ GEAR HOUSING (7.5 H.P
GENERAL
The information in this section is concerned with the removal repair and installation of the water pump, and gear train and shift mechanism of the gear housing RemovalTo remove the water pump from the gear housing proceed as follows :
AWARNING
Disconnect spark plug leads and ground them to support plate to prevent accidental starting of motor1Remove screw joining gear shift rods Figure 15
WATER PUMP
DescriptionThe water pump is located on top of the gear housing An impeller inside the pump body is attached to the driveshaft and is propelled directly by the engine The center of the rubber impeller is offset, causing the impeller vanes to flex as they rotate The impeller is sandwiched between the water pump body and water pump backplate creating sealAt slow speed, the impeller vanes push tightly against the outside circumference of the pump body forming seal there as well The volume (displacement) between any two vanes is least as they pass the outlet As they rotate and the volume (displacement) increased, the pressure will drop forming vacuum When the volume (displacement) is the greatest and the vacuum the highest, the leading vane goes past the inletthe vacuum will draw cooling water into the body and carry it to the outlet where it is pumped through the motor cooling systemFigure 14At low speeds, the pump is displacement pump, as motor speed increases, water resistance causes the vanes to flex in and it becomes centrifugal pump