Sierra Circulating Pump 18-3506-1, Replaces 46-879194401, for MerCruiser V6 4.3L MCM SN 1A063240 and Newer

The Sierra 18-3506-1 circulating pump is a direct-fit replacement water circulating pump built for MerCruiser V6 MCM engines, serial number 1A063240 (2007) and newer, on 4.3L engines without a water bypass hole. It uses a bi-directional brass impeller paired with a stainless steel shaft and stainless steel backing plate, giving the pump strong resistance to corrosion in the marine cooling system. The pump housing is designed to work with both stamped steel and composite timing covers, so it fits the timing cover configurations used across this engine family.

Every pump is inspected for fit, form, and function to dimensional standards before it ships, and each unit is finished with a vacuum test to confirm the seal holds properly. Mounting gaskets are included with the pump, so no separate gasket purchase is needed to complete the installation. This makes the 18-3506-1 a straightforward like-for-like swap for the factory circulating pump on qualifying MerCruiser 4.3L engines.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3506-1
• Product Type: Circulating Pump
• Material: Metal
• Impeller: Bi-directional brass impeller
• Shaft Material: Stainless steel
• Backing Plate Material: Stainless steel
• Timing Cover Compatibility: Stamped steel and composite
• Included Components: Circulating pump with mounting gaskets
• Weight: 10.69 pounds
• Vehicle Service Type: Boat
• Quality Testing: Vacuum tested for seal integrity, inspected for fit, form, and function

Fitment

• MerCruiser V6 MCM, serial number 1A063240 (2007) and newer
• 4.3L engines without a water bypass hole

Replaces (OEM)

• 46-879194401

Frequently Asked Questions

What engines does the Sierra 18-3506-1 circulating pump fit? It fits MerCruiser V6 MCM engines with serial number 1A063240 (2007) and newer, specifically 4.3L engines without a water bypass hole.

What OEM part number does the 18-3506-1 replace? This pump replaces MerCruiser OEM number 46-879194401.

Will this pump work on a 4.3L engine that has a water bypass hole? No. The 18-3506-1 circulating pump is built specifically for 4.3L MCM engines without a water bypass hole.

What is the impeller made of? The circulating pump uses a bi-directional brass impeller, which allows it to operate correctly regardless of pump rotation direction.

Are gaskets included with this pump? Yes, mounting gaskets are included with the 18-3506-1 circulating pump so it is ready to install.

How much does the circulating pump weigh? The Sierra 18-3506-1 weighs 10.69 pounds.

Does this pump fit both stamped steel and composite timing covers? Yes, the 18-3506-1 pump is designed to work with both stamped steel and composite timing covers.

Is the 18-3506-1 a genuine Sierra part? Yes, it is a Sierra manufactured circulating pump backed by Sierra's limited warranty.

How is the quality of this pump verified before shipping? Each 18-3506-1 pump is inspected for proper fit, form, and function, then finished with a vacuum test to confirm a proper seal.

What material is the pump shaft and backing plate made from? The shaft and backing plate on this circulating pump are stainless steel for corrosion protection.

Is the impeller direction-specific? No, the brass impeller in the 18-3506-1 is bi-directional, so it functions properly in either rotation direction.

What warranty comes with the 18-3506-1 circulating pump? The pump is covered by Sierra's limited warranty.