Sierra 18-3107 Impeller Plate, Replaces Mercury 54705 / 32768, for Mercury/Mariner 40 HP 4-Stroke Outboards

The Sierra 18-3107 Impeller Plate is an aluminum water pump component built for Mercury and Mariner 40 HP 4-stroke outboard motors with a 2:1 gear ratio, covering engines from serial number C159200 and up. The impeller plate sits within the lower unit water pump housing and works alongside the impeller to help maintain proper cooling water flow through the engine. It is manufactured to meet or exceed the fit, form, and function of the original equipment part it replaces, making it a straightforward drop-in replacement when servicing a worn or damaged water pump assembly.

This impeller plate is designed to be interchangeable with GLM 12520, Mallory 9-43407, and Mercury 54705 / 32768, so buyers who know any of those cross-reference numbers can confirm they are ordering the correct part. Because water pump service is fit-specific to the engine's serial number range and gear ratio, confirming these details before ordering helps ensure proper installation and cooling performance.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3107
• Material: Aluminum
• Weight: 0.03 pounds
• Engine Fitment: Mercury/Mariner 40 HP 4-stroke outboard, 2:1 gear ratio, serial number C159200 and up
• OEM Cross Reference: GLM 12520, Mallory 9-43407, Mercury 54705, 32768
• UPC: 030999315458

Fitment

• Mercury/Mariner 40 HP 4-stroke outboard, 2:1 gear ratio, serial number C159200 and up

Replaces (OEM)

• GLM 12520
• Mallory 9-43407
• Mercury 54705
• Mercury Marine 32768

Frequently Asked Questions

What engines does the Sierra 18-3107 impeller plate fit? The Sierra 18-3107 is designed for Mercury/Mariner 40 HP 4-stroke outboards with a 2:1 gear ratio, covering engines from serial number C159200 and up.

Is the 18-3107 the same as Mercury part number 54705? Yes, the Sierra 18-3107 impeller plate is interchangeable with Mercury 54705 as well as Mercury Marine 32768, GLM 12520, and Mallory 9-43407.

What is the 18-3107 impeller plate made of? The Sierra 18-3107 impeller plate is made of aluminum.

How much does the 18-3107 impeller plate weigh? The Sierra 18-3107 impeller plate weighs 0.03 pounds.

How do I know if the 18-3107 will fit my Mercury outboard? Fit depends on the engine's HP rating, gear ratio, and serial number, so check that your 40 HP 4-stroke Mercury/Mariner outboard has a 2:1 gear ratio and a serial number of C159200 or higher before ordering the 18-3107.

Can I use GLM 12520 or Mallory 9-43407 as a cross-reference for this part? Yes, GLM 12520 and Mallory 9-43407 are listed as interchangeable numbers for the Sierra 18-3107 impeller plate.

Is this an OEM part or an aftermarket replacement? The 18-3107 is a Sierra aftermarket impeller plate manufactured to meet or exceed the quality of the original Mercury equipment it replaces.

What comes with the Sierra 18-3107? The Sierra 18-3107 is sold as a single impeller plate.

Does the impeller plate come with the impeller itself? No, the 18-3107 is the impeller plate component only; it does not include the water pump impeller.

What gear ratio is required for the 18-3107 impeller plate to fit? The Sierra 18-3107 is built for a 2:1 gear ratio on applicable 40 HP 4-stroke Mercury/Mariner outboards.

Is Sierra 32768 the same part as the 18-3107? Mercury Marine 32768 is one of the OEM cross-reference numbers that the Sierra 18-3107 impeller plate is designed to replace.