Sierra 18-3104-1 Water Pump Impeller for Johnson/Evinrude 40 HP (1989-98) and 48 HP (1989-96) Outboards

The Sierra 18-3104-1 is a rubber water pump impeller built for Johnson/Evinrude (OMC/BRP) outboard cooling systems. The impeller is the wear component inside the outboard's lower unit water pump that draws raw water in and forces it through the cooling passages to keep the engine block and exhaust running at safe operating temperatures. Made from black rubber, it is engineered to meet or exceed the specifications of the original equipment part it replaces, restoring proper coolant flow when the factory impeller has worn, glazed, or lost its vanes.

This impeller is a direct fit for Johnson/Evinrude 40 HP outboards from 1989-98 and 48 HP outboards from 1989-96, and it cross-references to a number of common OEM and aftermarket part numbers, making it easy to identify against whatever number appears on your old impeller or parts diagram. Replacing the water pump impeller on schedule (or any time overheating, reduced water flow, or a weak telltale stream is noticed) helps prevent overheating damage to the powerhead.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3104-1
• Material: Rubber
• Color: Black
• Engine Application: Johnson/Evinrude (OMC/BRP) outboard cooling system
• Package Dimensions: 7.13 L x 1.25 H x 6 W (inches)
• Weight: 0.26 pounds
• Country of Origin: Taiwan, Province Of China

Fitment

• Johnson/Evinrude 40 HP, 1989-98
• Johnson/Evinrude 48 HP, 1989-96

Replaces (OEM)

• GLM 89790
• Johnson/Evinrude Outboard 432941
• Johnson/Evinrude Outboard 437059
• Johnson/Evinrude Outboard 765350
• Mallory 9-45204
• Mallory 9-45204-10
• Mallory 9-45211

Frequently Asked Questions

What outboards does the Sierra 18-3104-1 impeller fit? The Sierra 18-3104-1 fits Johnson/Evinrude outboards rated 40 HP for model years 1989-98 and 48 HP for model years 1989-96.

Is the 18-3104-1 an OEM Johnson/Evinrude part or an aftermarket replacement? It is a Sierra aftermarket impeller manufactured to meet or exceed the specifications of the original Johnson/Evinrude equipment it replaces, rather than an OEM-branded part.

What OEM part numbers does the Sierra 18-3104-1 cross-reference to? This impeller cross-references to GLM 89790, Johnson/Evinrude Outboard numbers 432941, 437059, and 765350, and Mallory 9-45204, 9-45204-10, and 9-45211.

What material is the impeller made from? The 18-3104-1 impeller is made from black rubber, the standard material for outboard water pump impeller vanes.

How much does the 18-3104-1 impeller weigh? The Sierra 18-3104-1 weighs 0.26 pounds.

What are the package dimensions of the 18-3104-1? The Sierra 18-3104-1 ships in packaging measuring 7.13 L x 1.25 H x 6 W inches.

How do I know when to replace my outboard's water pump impeller? Signs that the impeller in your Johnson/Evinrude water pump needs replacement include engine overheating, a weak or absent telltale (pee stream) at idle, or reduced raw water flow through the cooling system; the Sierra 18-3104-1 is sized for 40 HP (1989-98) and 48 HP (1989-96) applications showing these symptoms.

Does the 18-3104-1 include a full water pump repair kit? The 18-3104-1 is the impeller itself; it does not include the housing, wear plate, or gaskets that make up a complete water pump kit.

Where is the Sierra 18-3104-1 impeller manufactured? The 18-3104-1 impeller is manufactured in Taiwan, Province Of China.

What color is the 18-3104-1 impeller? The 18-3104-1 is black.

Will the 18-3104-1 work on any outboard brand? No, the 18-3104-1 is specifically designed for Johnson/Evinrude (OMC/BRP) outboard cooling systems in the 40 HP (1989-98) and 48 HP (1989-96) ranges.