How to Repair a Water Pump on an Outboard
Water pumps on outboard motors are typically of 'flexible vane' construction. The vane or impeller is made from somewhat flexible rubber reinforced with fiber which rotates inside a round housing, drawing water through a hole on one side and pushing it out a hole on the other side with great force. The impeller is vulnerable to damage from foreign materials such as sand or grit being drawn into the cooling system and also to dry-rot.
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Things You'll Need
- Mechanics tools
- Rubber or rawhide hammer
- Rebuild kit (impeller and seals)
- Anti-seize
- Marine grease
- Lower unit oil
Instructions
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Removing the Pump
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1
Drain the oil from the lower unit. Shift into forward gear with the gearshift. Remove the gearshift linkage at the lower unit (LU).
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2
Remove all bolts holding the LU to the motor leg and slide the LU down off of the engine driveshaft. Remove the old driveshaft seal and discard it. Check for any missed fasteners if the LU case will not separate from the leg. Rap gently with a soft hammer such as rubber of rawhide if all of the fasteners are removed and the LU will not budge. Save the gasket, if possible.
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3
Remove the bolts holding the water pump cap and housing down, then lift up the housing, cap, pump and bottom plate. Inspect the housing for heavy scoring or pitting that may prevent proper operation and replace if necessary.
Re-Assembly
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4
Install the new driveshaft o-ring and lightly grease the shaft splines as well as the inside of the pump housing. Bolt the housing back down.
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5
Slide the new impeller hub onto the shaft. Once the impeller begins to engage the edge of the housing, rotate the impeller in the direction it would normally turn to 'load up' the vanes and collapse them enough to get the impeller into the housing. Align the shaft key with the hub slot and push the impeller home once the impeller is well started into the housing. Reinstall the cap.
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6
Reinstall the LU gasket and align the water lines from the LU to the motor leg. Push the LU into position and bolt it down. Apply a little anti-seize to these bolts to make them come out easier the next time. Torque to recommended specifications and do not over torque.
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7
Refill the LU oil reservoir with fresh oil and replace the LU drain and fill plug gaskets. Refer to original equipment manufacturer's recommendations for oil type and fill procedure.
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