Chrysler 20 and 30 HP Outboard Motors Service Manual OB 3435, Page 180Get this manual
Subsection _ GEAR HOUSING
GENERAL
This section deals with the removal, repair and installation of the water pump, gear train and shift mechanism of the gear housing When the volume (displacement) is greatest, the vacuum highest and the leading vane goes past the inlet, the vacuum will draw cooling water into the body and carry it to the outlet where it is pumped through the motor cooling system At low speeds, the pump is displacement pump As motor speed increaseswater resistance causes the vanes to flex in and it becomes centrifugal pumpLOW SPEED HIGH SPEED
WATER PUMP
DescriptionThe water pump is found on the top of the gear housingAn impeller inside the pump body is attached to the riveshaft and is propelled directly by the engine