Description
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
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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.
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Marine-Grade Materials: Ethanol-resistant gaskets and seals designed to withstand modern E10 fuels that can degrade older rubber components.
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Precision Fit: Manufactured to exact OEM tolerances for proper float height, fuel metering, and leak-free assembly.
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Replaces OEM Numbers: Compatible with Sierra 18-7768, Mallory 9-37503, 6H4-W0093-03-00, 6H4-W0093-02-00.
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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
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Work clean: Disassemble on a clean white towel to catch small parts. Photograph each step for reference.
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Soak and clean: Use carburetor cleaner to soak the disassembled body and jets. Blow compressed air through all passages.
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Replace in order: Follow the gasket sequence — float bowl gasket last so the float height stays correct during assembly.
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Check float height: Verify float level specification before closing the bowl. Incorrect float height = rich or lean condition.
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Prime before starting: Squeeze the primer bulb until firm before cranking. It may take several pulls to fill the rebuilt carb with fuel.
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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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