191
COOLING SYSTEM
COMPONENTS
10
COMPONENTS
Water Pump and Intakes
External water intakes mounted in the gearcase
housing collect water and must supply the inlet
side of the water pump with an unrestricted and
unaerated water supply. Water is drawn into the
water pump through a hole in the lower plate of
the water pump assembly. All cooling water to the
powerhead is provided by the water pump.
• A nylon wedge (impeller key) is used to engage
the impeller bushing and driveshaft.
• The nylon impeller housing with liner must seal
against a separate water pump plate.
• The bottom plate MUST seal to gearcase.
• The pump operates as a positive displacement
pump at LOW speeds (below 1500 RPM) and
as a centrifugal pump at HIGHER speeds.
Refer to WATER PUMP SERVICE on p. 263 for
servicing.
Water Supply Tube
The water pump outlet connects with the water
supply tube located in the outboard’s midsection.
Grommets seal the water tube to the water pump
housing and the adaptor housing. The water tube
fastens to the base of the adapter housing with a
retainer plate and screws.
Water supplied to the water tube provides all cool-
ing water to the adapter housing and cylinder
block.
Adapter/Inner Exhaust Housing
• Adapts the cylinder/crankcase assembly (pow-
erhead) to the exhaust housing and the water
tube.
• Provides water passages which route incoming
and outgoing cooling water.
• Provides exhaust passages which connect to
the gearcase.
1. Water inlet
2. Water outlet
3. Seal
4. Plate
5. O-ring
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1. Megaphone
2. Exhaust housing
3. Water tube
4. Adapter housing
5. Inner exhaust housing
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