Sierra 18-3446 Water Pump Kit - Replaces Mercury 46-70941A3 - Fits 4/4.5 HP 1-Cylinder Outboards

The Sierra 18-3446 Water Pump Kit is a complete impeller service kit built for 4 HP and 4.5 HP, 1-cylinder outboard motors that use a.456 inch I.D. Water impeller. This kit is the go-to fix when an outboard starts running hot or loses its telltale water stream, since the impeller and impeller plate are the two components that wear out and cause cooling failures over time.

Inside the kit you get a matched pair of parts designed to work together: the impeller (Sierra 18-3039, O.E. #47-89981) and the impeller plate (Sierra 18-3139, O.E. #46895). Replacing both at the same time, rather than the impeller alone, restores proper water pump sealing and flow, since a worn plate can cause a new impeller to fail prematurely.

The Sierra 18-3446 is built to meet or exceed the original equipment part it replaces and is a direct interchange for Mercury 46-70941A3, so it installs in place of the original Mercury water pump kit without modification. It is sized specifically for 4 HP and 4.5 HP, 1-cylinder outboards using the.456 inch I.D. Water impeller design, making it important to confirm your impeller bore diameter before ordering.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3446
• Product Type: Water Pump Kit
• Horsepower Fitment: 4 HP and 4.5 HP
• Cylinder Configuration: 1 cylinder outboard motors
• Water Impeller Inside Diameter: 0.456 inch
• Kit Contents: Impeller (18-3039), Impeller Plate (18-3139)
• Impeller OEM Part Number: 47-89981
• Impeller Plate OEM Part Number: 46895
• OEM Cross Reference: 46-70941A3
• Weight: 0.4 pounds
• UPC: 808282111939

Fitment

• 4 HP and 4.5 HP, 1-cylinder outboard motors with a.456 inch I.D. Water impeller

Replaces (OEM)

• 46-70941A3

Frequently Asked Questions

What does the Sierra 18-3446 water pump kit include? The kit includes an impeller (Sierra 18-3039, O.E. #47-89981) and an impeller plate (Sierra 18-3139, O.E. #46895), the two components needed to rebuild the water pump on a compatible outboard.

What outboards does the Sierra 18-3446 fit? This kit fits 4 HP and 4.5 HP, 1-cylinder outboard motors that use a.456 inch I.D. Water impeller.

Is the Sierra 18-3446 a direct replacement for Mercury 46-70941A3? Yes, the Sierra 18-3446 water pump kit is interchangeable with Mercury 46-70941A3.

How do I know if my impeller needs replacing? A weak or absent telltale water stream, an overheating outboard, or a rubber impeller with cracked or worn vanes are signs that the water pump kit, such as the Sierra 18-3446, needs replacement.

Should I replace the impeller plate along with the impeller? Yes, the Sierra 18-3446 kit pairs the impeller with the impeller plate because a worn plate can cause a newly installed impeller to fail early, so both parts are replaced together.

Does the Sierra 18-3446 meet original equipment quality standards? Sierra states this water pump kit meets or exceeds the original equipment part it replaces, namely Mercury 46-70941A3.

What is the water impeller bore size on the Sierra 18-3446 kit? The impeller in this kit has a.456 inch inside diameter, which is specific to the 4 HP and 4.5 HP, 1-cylinder outboards it is designed for.

How much does the Sierra 18-3446 water pump kit weigh? The Sierra 18-3446 water pump kit weighs 0.4 pounds.

Can this kit be used on multi-cylinder outboards? No, the Sierra 18-3446 is designed for 1-cylinder outboard motors in the 4 HP and 4.5 HP range with a.456 inch I.D. Water impeller, not multi-cylinder engines.

What is the OEM part number that the Sierra 18-3039 impeller replaces? The impeller included in the Sierra 18-3446 kit, part 18-3039, replaces O.E. Part number 47-89981.

What is the OEM part number that the impeller plate replaces? The impeller plate in the Sierra 18-3446 kit, part 18-3139, replaces O.E. Part number 46895.