Sierra Carburetor Kit 18-7728 for Mercruiser H4/4150 R6647A Carburetors

The Sierra 18-7728 is a carburetor kit built to rebuild and restore Mercruiser carburetors coded H4/4150 and R6647A, matched to serial number range 6083145-B816540. Over time, carburetor gaskets, needles, and seals wear out or degrade from ethanol-blended fuel exposure, leading to rough idle, flooding, or poor fuel metering. This kit supplies the internal wear components needed to bring the carburetor back to proper operating condition without replacing the entire unit, which is a more economical and time-efficient repair path for boat owners and marine technicians. Note that this kit does not include metering rods, so those should be inspected separately and sourced individually if worn. Installation follows standard carburetor rebuild procedure: the carburetor is removed from the intake, disassembled, cleaned, and the kit components are installed in place of the worn originals before reassembly and reinstallation. The kit is packaged for a single carburetor rebuild and is intended for use by anyone comfortable performing a carburetor overhaul, from DIY boat owners to marine service shops. Always match the kit to the correct carburetor code and serial number range before ordering to ensure proper fit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7728
• Product Type: Carburetor Kit
• Application: Mercruiser, Carb Code H4/4150, R6647A
• Serial Number Range: 6083145-B816540
• Includes Metering Rods: No
• UPC: 747730045382
• Weight: 0.46 pounds

Fitment

• Mercruiser carburetors, Carb Code H4/4150, R6647A, Serial Number 6083145-B816540

Replaces (OEM)

• No OEM cross-reference numbers are listed for this kit.

Frequently Asked Questions

What carburetor does the Sierra 18-7728 kit fit? The Sierra 18-7728 carburetor kit fits Mercruiser carburetors with Carb Code H4/4150 or R6647A, within the serial number range 6083145-B816540.

Does the 18-7728 kit include metering rods? No, the Sierra 18-7728 carburetor kit does not include metering rods; those must be sourced separately if replacement is needed.

How much does the 18-7728 carburetor kit weigh? The Sierra 18-7728 carburetor kit weighs 0.46 pounds.

Is the 18-7728 kit enough to fully rebuild a carburetor? It supplies the wear components needed for a standard rebuild of a matching H4/4150 or R6647A Mercruiser carburetor, aside from the metering rods, which are not included in the 18-7728 kit.

How do I confirm my carburetor matches this kit before ordering? Check your carburetor's stamped code against H4/4150 or R6647A and confirm the engine serial number falls within 6083145-B816540, the application range for the Sierra 18-7728 kit.

Can I install the 18-7728 kit myself? Yes, the Sierra 18-7728 kit is installed using standard carburetor rebuild steps: remove and disassemble the carburetor, clean it, install the kit components, then reassemble and reinstall.

What is the UPC for the Sierra 18-7728 carburetor kit? The UPC for the Sierra 18-7728 carburetor kit is 747730045382.

Is the Sierra 18-7728 an OEM part or an aftermarket kit? The Sierra 18-7728 is a Sierra-branded carburetor kit designed as a rebuild kit for the specified Mercruiser carburetor codes, not an OEM Mercruiser-branded part.

What is included in the Sierra 18-7728 carburetor kit box? The box contains the internal rebuild components for the specified Mercruiser H4/4150 and R6647A carburetors, excluding metering rods.

Will the 18-7728 kit work on any Mercruiser carburetor? No, the Sierra 18-7728 kit is matched specifically to Carb Code H4/4150 or R6647A carburetors within serial number range 6083145-B816540, not all Mercruiser carburetors.