Sierra 18-3448 Water Pump Kit, Replaces Mercury 46-48744A3, Fits 20 HP Outboards 1967-80

The Sierra 18-3448 Water Pump Kit is a complete outboard water pump rebuild kit designed for 20 HP outboard motors from 1967-80. This kit replaces the OEM Mercury part number 46-48744A3 and restores proper cooling system function to an aging or worn water pump assembly. Weak or failing water pump components are a common cause of overheating in older outboards, and this kit provides the core parts needed to bring the pump back to factory-correct operation in a single service.

Inside the kit, boaters get the impeller, the wear item that actually pumps raw water through the cooling passages, along with the upper face plate gasket and other pump housing gaskets needed to reseal the assembly during reinstallation. The impeller and gaskets are manufactured to Sierra's standard specifications so the rebuilt pump seals and pumps correctly without leaks or premature wear. The kit is built from metal and rubber components sized specifically for this pump housing, so no additional fabrication or modification is needed during the rebuild.

This kit is intended for outboard owners and marine technicians performing a routine water pump service or repair on a 20 HP outboard covered by this application. Because the impeller is a rubber wear part, it is good practice to replace it any time the lower unit is opened for other service, even if the old impeller looks intact.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3448
• Product Name: Water Pump Kit
• Replaces (OEM): 46-48744A3
• Fits: Mercury 20 HP outboards, 1967-80
• Material: Metal
• Weight: 0.66 pounds
• Unit Count: 1 kit
• Kit Contents: Impeller (18-3052, O.E. 47-89982), Upper Face Plate Gasket (18-2827, O.E. 27-39623), Lower Water Pump Gasket (18-2828), Water Pump Gasket (18-2829)

Fitment

• Mercury 20 HP outboards, 1967-80

Replaces (OEM)

• 46-48744A3

Frequently Asked Questions

What does the Sierra 18-3448 Water Pump Kit fit? The Sierra 18-3448 Water Pump Kit fits Mercury 20 HP outboards built from 1967 to 1980.

Is the Sierra 18-3448 a direct replacement for Mercury 46-48744A3? Yes, the Sierra 18-3448 Water Pump Kit replaces Mercury part number 46-48744A3 and is built to fit the same 20 HP outboard water pump housing.

What parts are included in the 18-3448 kit? The kit contains an impeller (Sierra 18-3052, O.E. 47-89982), an upper face plate gasket (Sierra 18-2827, O.E. 27-39623), a lower water pump gasket (18-2828), and a water pump gasket (18-2829).

How much does the Sierra 18-3448 Water Pump Kit weigh? The Sierra 18-3448 Water Pump Kit weighs 0.66 pounds.

What material is the impeller in this kit made from? The components in the Sierra 18-3448 Water Pump Kit, including the impeller, are made from metal and rubber materials sized for the 20 HP outboard water pump housing.

Do I need to replace the impeller even if it still looks fine? Yes, since the impeller included in the Sierra 18-3448 kit is a rubber wear part, it is best practice to replace it whenever the water pump housing is opened for service, regardless of its visual condition.

Will this kit fix an overheating 20 HP Mercury outboard? A worn impeller or damaged pump gaskets are a common cause of outboard overheating, and the Sierra 18-3448 Water Pump Kit provides the impeller and gaskets needed to restore proper cooling pump function on the 20 HP Mercury application it covers.

Is the Sierra 18-3448 kit genuine Sierra or aftermarket? The 18-3448 Water Pump Kit is manufactured by Sierra as a direct-fit replacement kit for the Mercury 46-48744A3 water pump on 20 HP outboards from 1967-80.

Does the kit include the gasket for the water pump housing? Yes, the Sierra 18-3448 kit includes the upper face plate gasket, lower water pump gasket, and water pump gasket needed to reseal the housing along with the impeller.

What is the OEM cross-reference number for this water pump kit? The Sierra 18-3448 Water Pump Kit cross-references to Mercury OEM part number 46-48744A3.

Can I install the Sierra 18-3448 kit myself? The Sierra 18-3448 Water Pump Kit contains the impeller and gaskets needed for a standard water pump rebuild on a 20 HP outboard, a job commonly performed by boat owners and marine technicians during routine lower unit service.

How many units come in one Sierra 18-3448 kit? One Sierra 18-3448 Water Pump Kit contains a single set of the impeller and gaskets listed for the 20 HP Mercury outboard application.