Chrysler 70, 75 and 85 HP Outboard Motors Service Manual OB 3438, Page 170Get this manual
Subsection
_ SINGLE PIECE GEAR HOUSING
GENERAL
The information in this section concerns the removal, repair and installation of the water pump, gear train and shift mechanism of the single piece gear housing they pass the outlet As they rotate and the volume (displacement) increasesthe pressure dropsforming vacuum When the volume (displacement) is the greatest and the vacuum highest, the leading vane goes past the inlet and the vacuum draws cooling water into the body and carries it to the outlet where it is pumped through the motor cooling system Figure 1
WATER PUMP
DescriptionThe water pump is located on top of the gear housingAn impeller inside the pump body is attached to the driveshaft and is propelled directly by the engine