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.
Refer to WATER PUMP SERVICE on p. 282 for servicing.
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- Water inlet
- Water outlet
- Seal
- Plate
IMPORTANT: The water pump housing includes a small vent hole to the side of the water outlet. Be sure to use the correct parts when replacing the water pump.
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1.Hole
Exhaust Housing
The water pump outlet connects with a water tube and passages located in the outboard’s midsection. Grommets seal the water pump housing to the water tube and the water tube to the exhaust housing.
Water supplied to the exhaust housing provides all cooling water to the cylinder block.
Pressure Relief Valve
A pressure relief valve is used to control water flow and operating temperature at higher speeds (above approximately 2800 RPM). The pressure relief valve opens as water pressure increases. Spring tension sets the opening pressure.
Overheating: A restricted or faulty valve typically results in HIGH SPEED overheating.
Overcooling: Debris may prevent the valve from closing completely.
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Pressure relief valve components
Thermostat
The thermostat controls water flow and operating temperature at lower speeds (below 1800 RPM).
Overheating: A restricted or faulty thermostat typically results in LOW SPEED overheating.
Overcooling: Debris may prevent the thermostat from closing completely.
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- Spring, thermostat and gasket
- Cylinder head
