Sierra 18-3414 Water Pump Base for Mercury/Mariner Outboard Motors - Replaces 46-77516A1

The Sierra 18-3414 is a water pump base built for Mercury/Mariner outboard motors, designed to meet or exceed original equipment quality. The water pump base is a core structural component of the outboard's cooling system, forming the housing that the impeller and related water pump components mount into and seal against. A properly fitted water pump base ensures the impeller can maintain the seal and pressure needed to draw raw water through the powerhead cooling passages, so replacing a cracked, worn, or corroded base restores reliable water flow and helps protect the engine from overheating.

Sierra manufactures this base as a direct cross-reference to several Mercury OEM part numbers, making it straightforward to identify as the correct replacement when servicing Mercury/Mariner outboards that originally used any of those OEM numbers. At 0.21 pounds, it is a compact, precision-made component intended to be installed alongside the impeller and related water pump hardware during a cooling system service or rebuild.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3414
• Product Type: Water Pump Base
• Weight: 0.21 pounds
• UPC: 030999315885
• Fitment: Mercury/Mariner outboard motor
• OEM Cross-Reference: 46-77516A1, 46-73842A2, 46-68390A1, 46-65498A1, 46-48745A1

Fitment

• Mercury/Mariner outboard motor

Replaces (OEM)

• 46-77516A1
• 46-73842A2
• 46-68390A1
• 46-65498A1
• 46-48745A1

Frequently Asked Questions

What is the Sierra 18-3414 water pump base used for? It is the water pump base for Mercury/Mariner outboard motor cooling systems, the housing component that the impeller and water pump assembly mount into to draw and seal raw water for engine cooling.

Which Mercury outboard motors does part 18-3414 fit? The Sierra 18-3414 water pump base is built for Mercury/Mariner outboard motors that use any of its cross-referenced Mercury OEM part numbers: 46-77516A1, 46-73842A2, 46-68390A1, 46-65498A1, or 46-48745A1.

Is Sierra 18-3414 the same as Mercury 46-77516A1? Yes, the Sierra 18-3414 water pump base cross-references directly to Mercury OEM part numbers 46-77516A1, 46-73842A2, 46-68390A1, 46-65498A1, and 46-48745A1, so it is an equivalent replacement for any of those numbers.

How much does the 18-3414 water pump base weigh? The Sierra 18-3414 water pump base weighs 0.21 pounds.

Does the 18-3414 come with the impeller included? No, the Sierra 18-3414 is the water pump base only; the impeller and drain gasket are separate components sold under their own part numbers.

What OEM part numbers does the Sierra 18-3414 replace? It replaces Mercury OEM numbers 46-77516A1, 46-73842A2, 46-68390A1, 46-65498A1, and 46-48745A1.

Is the Sierra 18-3414 an aftermarket or genuine Mercury part? The Sierra 18-3414 is an aftermarket water pump base manufactured to meet or exceed original equipment quality, offered as a cross-reference replacement for the listed Mercury OEM part numbers rather than a Mercury-branded part.

How do I confirm the 18-3414 is the correct water pump base for my outboard? Check the OEM number stamped on your existing water pump base against the cross-reference list for Sierra 18-3414 (46-77516A1, 46-73842A2, 46-68390A1, 46-65498A1, 46-48745A1); a match confirms fit is specific to those numbers.

What UPC is associated with the Sierra 18-3414 water pump base? The UPC for the Sierra 18-3414 water pump base is 030999315885.

Why would I need to replace a water pump base on my outboard motor? A cracked, worn, or corroded water pump base can prevent the impeller from sealing properly, reducing raw water flow to the cooling system; replacing it with the Sierra 18-3414 restores the sealing surface needed for reliable cooling.