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. 294, or WATER PUMP SERVICE on p. 316 for servicing
001216
001217
- Water inlet
- Water outlet
- Seal
- Plate
IMPORTANT: The water pump housing on 2 cylinder models includes a small hole to the rear of the water outlet. This hole provides cooling water for the tip of the exhaust passage. Be sure to use the correct parts when replacing the water pump.
004970
- Hole
Exhaust Housing
2-CYLINDER MODELS
The water pump outlet connects with passages located in the outboard’s midsection. A grommet seals the water pump housing to the exhaust housing.
Water supplied to the exhaust housing provides all cooling water to the cylinder block.
Water Supply Tube
3-CYLINDER MODELS
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 cooling water to the adapter housing and cylinder block.
Adapter/Inner Exhaust Housing
3-CYLINDER MODELS
- Adapts the cylinder/crankcase assembly (powerhead) 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.
002436
- Megaphone
- Exhaust housing
- Water tube
- Adapter housing
- Inner exhaust housing
Pressure Relief Valve
A pressure relief valve is used to control water flow and operating temperature at higher speeds (above approximately 1800 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.
002437
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.
002439
- Cover and O-ring
- Spring and thermostat
- Cylinder head
- Cylinder head seal
Block Venting
A fitting and hose connected to the top of the exhaust cover allows the constant movement of water and/or air from the block. Circulated water flows through the EMM and vapor separator before exiting through the overboard indicator.
002478
2-Cylinder models
- Fitting
002440
3-Cylinder models
- Fitting
Water Pressure Connection
A fitting and hose for an accessory water pressure gauge can be connected at the top of the cylinder block next to the pressure valve housing.
002461
1.Fitting
