Complete Carburetor Repair Kit for 40-50HP 2-Stroke Outboard Engines
The iFJF 18-7768 carburetor repair kit provides everything needed to rebuild and restore the carburetor on 40-50HP 2-stroke outboard marine engines. This comprehensive kit replaces worn gaskets, seals, needle valves, and o-rings — restoring proper fuel metering, idle quality, and throttle response. Compatible with Mercury, Mariner, and other outboards using Tohatsu-sourced powerheads of this era.
Key Features
Complete Rebuild Kit: Includes all gaskets, o-rings, inlet needle & seat, float bowl gasket, welch plugs, and mixture screw o-ring — everything needed for a full carburetor overhaul.
Marine-Grade Materials: Ethanol-resistant gaskets and seals designed to withstand modern E10 fuels that can degrade older rubber components.
Precision Fit: Manufactured to exact OEM tolerances for proper float height, fuel metering, and leak-free assembly.
Replaces OEM Numbers: Compatible with Sierra 18-7768, Mallory 9-37503, 6H4-W0093-03-00, 6H4-W0093-02-00.
Restores Performance: Fixes common symptoms like hard starting, rough idle, bogging on acceleration, and fuel leaks from bowl gasket deterioration.
Compatibility
Engine
HP Range
Notes
Mercury / Mariner 2-Stroke
40HP, 45HP, 50HP
Late 1980s-1990s models (verify carb model)
Tohatsu 2-Stroke
40HP, 50HP
OEM equivalent fitment
Yamaha 2-Stroke
40HP, 50HP
Select models — verify carburetor type
Cross-Reference Part Numbers
Brand
Part Number
Sierra Marine
18-7768
Mallory Marine
9-37503
Yamaha OEM
6H4-W0093-03-00, 6H4-W0093-02-00
GLM Marine
40310
When to Rebuild Your Carburetor
2-stroke outboard carburetors are precision instruments that meter fuel based on airflow. Over time, the rubber gaskets, o-rings, and float needle seats degrade — especially when exposed to ethanol-blended fuels. A rebuild kit like the iFJF 18-7768 restores factory-spec fuel delivery without the cost of a complete carburetor replacement.
Common symptoms indicating a carburetor rebuild is needed:
Engine cranks but won't start (fuel not reaching cylinders)
Rough or surging idle (vacuum leak from dried gaskets)
Bogging or hesitation on acceleration (clogged jets or worn accelerator pump)
Fuel leaking from carburetor body (failed float bowl gasket)
Engine runs only with choke partially engaged
Excessive fuel consumption or fouled spark plugs
Installation Tips
Work clean: Disassemble on a clean white towel to catch small parts. Photograph each step for reference.
Soak and clean: Use carburetor cleaner to soak the disassembled body and jets. Blow compressed air through all passages.
Replace in order: Follow the gasket sequence — float bowl gasket last so the float height stays correct during assembly.
Check float height: Verify float level specification before closing the bowl. Incorrect float height = rich or lean condition.
Prime before starting: Squeeze the primer bulb until firm before cranking. It may take several pulls to fill the rebuilt carb with fuel.
Synchronize if twin: On dual-carb applications, adjust linkage so both throttle plates open simultaneously.
Frequently Asked Questions
Q: Does this kit fit my specific 50HP Mercury outboard?A: This kit fits 40-50HP Mercury/Mariner 2-stroke outboards from the late 1980s through 1990s. To confirm, check your carburetor model number (stamped on the carb body) or verify your engine serial number against the Sierra 18-7768 application guide. Contact us with your serial number if uncertain.
Q: What's included in the kit?A: Complete set includes: float bowl gasket, inlet needle & seat assembly, mixture screw o-ring, welch/expansion plugs, bowl drain screw gasket, fuel inlet gasket, and all body-to-manifold gaskets. Everything needed for one carburetor.
Q: Can I use this kit if I run E10 (10% ethanol) fuel?A: Yes. The gaskets and seals in this kit are formulated to resist ethanol-related deterioration. However, we still recommend using ethanol-free marine fuel when available, as ethanol attracts moisture and accelerates corrosion in marine environments.
Q: How difficult is a carburetor rebuild for a DIYer?A: Moderate difficulty. If you can change a water pump impeller or lower unit oil, you can rebuild a 2-stroke carburetor. The key is cleanliness and organization. Budget 1-2 hours for your first rebuild. Watch a model-specific video tutorial before starting.
Q: Do I need any special tools?A: Basic metric socket set, flathead and Phillips screwdrivers, needle-nose pliers, carburetor cleaner spray, and compressed air are sufficient. A carburetor jet cleaning tool set is helpful but not required.
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