Sierra Water Pump Kit 18-3322 - Replaces 46-77516A3 - Fits Mercury 35/40/50/65 HP Outboards Prior to 1976

The Sierra 18-3322 Water Pump Kit is a complete water pump rebuild kit for Mercury outboard engines, designed to restore proper cooling system function on outboards that rely on a mechanically driven impeller pump to circulate raw water through the powerhead. Weak or worn water pump components are a leading cause of overheating in outboard motors, and this kit bundles the core wear parts needed to rebuild the pump in one purchase rather than sourcing each piece individually. The kit centers on a replacement impeller, which is the rubber-vaned component that physically pushes cooling water through the engine and is the part most prone to wear, cracking, or heat damage over time. Alongside the impeller, the kit supplies the upper water pump housing that the impeller rotates inside of, and the water pump base that mounts the assembly to the lower unit. Because housing wear and base wear both contribute to reduced pump pressure even after an impeller swap, replacing all three components together helps restore full cooling performance rather than masking the problem with a partial fix. This kit is built for various Mercury 35 HP, 40 HP, 50 HP, and 65 HP outboard engines prior to 1976, and it directly replaces Mercury Marine water pump kit 46-77516A3, making it a straightforward drop-in equivalent for boaters maintaining these older Mercury outboards. Each component in the kit carries its own Sierra part number, so individual pieces can be identified and reordered separately if only one wears out in the future.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3322
• Product Type: Water Pump Kit
• Weight: 0.51 pounds
• Kit Contents: Impeller (O.E. 47-89983, Sierra 18-3007, qty 1); Upper Water Pump Housing (O.E. 46-77822A1, Sierra 18-3118, qty 1); Water Pump Base (O.E. 46-77516A1, Sierra 18-3422, qty 1)
• Replaces (OEM): 46-77516A3
• Fitment: Various Mercury 35/40/50/65 HP outboard engines, prior to 1976

Fitment

• Various Mercury 35 HP, 40 HP, 50 HP, and 65 HP outboard engines, prior to 1976

Replaces (OEM)

• 46-77516A3

Frequently Asked Questions

What is included in the Sierra 18-3322 Water Pump Kit? The 18-3322 kit includes an impeller (O.E. 47-89983, Sierra 18-3007), an upper water pump housing (O.E. 46-77822A1, Sierra 18-3118), and a water pump base (O.E. 46-77516A1, Sierra 18-3422), one of each.

What engines does this water pump kit fit? Sierra 18-3322 fits various Mercury 35 HP, 40 HP, 50 HP, and 65 HP outboard engines, prior to 1976.

Does the 18-3322 kit replace Mercury Marine part 46-77516A3? Yes, the Sierra 18-3322 Water Pump Kit is a direct replacement for Mercury Marine 46-77516A3.

How much does the water pump kit weigh? The Sierra 18-3322 Water Pump Kit weighs 0.51 pounds.

Will Sierra 18-3322 fit a Mercury outboard made after 1976? No, the fitment for this kit is specified as various Mercury 35/40/50/65 HP outboard engines prior to 1976 only.

What is the OEM number for the impeller in this kit? The impeller included in the Sierra 18-3322 kit corresponds to O.E. Number 47-89983 and is also sold separately as Sierra 18-3007.

Is the water pump base included as a separate piece? Yes, the kit includes a water pump base, O.E. Number 46-77516A1, also available separately as Sierra 18-3422.

Why replace the housing and base along with the impeller instead of just the impeller alone? Wear on the upper water pump housing and base in the 18-3322 kit can reduce pump pressure even with a new impeller installed, so replacing all three restores full cooling system performance.

What does the O.E. 46-77822A1 part correspond to in this kit? O.E. 46-77822A1 is the upper water pump housing included in the Sierra 18-3322 kit, listed as Sierra 18-3118.

Can individual components of the 18-3322 kit be reordered separately if only one part wears out? Yes, each component has its own Sierra part number: 18-3007 for the impeller, 18-3118 for the upper housing, and 18-3422 for the base, so any single piece can be reordered on its own.