853720T15 853720T21 8M0109535 Carburetor Assembly for Mercury Mariner | JLM Marine

Carburetor Assembly 853720T15 853720T21 8M0109535 – Fits Mercury Mariner 4-Stroke 15-20 HP Outboards

This carburetor assembly is engineered for Mercury Mariner 4-stroke 2-cylinder outboard engines rated 15-20 HP. It provides reliable fuel delivery for remote-control models within the specified serial number ranges, ensuring smooth engine performance and consistent throttle response.

This part directly replaces OEM numbers 853720T15, 853720T21, and 8M0109535, offering a cost-effective solution for carburetor rebuilds or replacements on compatible Mercury Mariner outboards.

• Complete carburetor assembly ready for installation
• Designed for 4-stroke 2-cylinder Mercury Mariner engines
• Fits 15-20 HP remote-control models with specific serial ranges

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1 × Carburetor Assembly 853720T15

Installation Guide

1. Disconnect the fuel line from the engine and remove the air intake cover. Ensure the engine is cool and the ignition is off.
2. Disconnect the throttle and choke linkages from the old carburetor, noting their positions for reassembly. Take photos if needed for reference.
3. Remove the mounting bolts securing the carburetor to the intake manifold. Carefully lift the old carburetor away from the engine.
4. Inspect the intake manifold gasket and replace if damaged or worn. Clean the mounting surface thoroughly to ensure a proper seal.
5. Position the new carburetor assembly onto the intake manifold, aligning the mounting holes. Install and hand-tighten the mounting bolts evenly.
6. Torque the carburetor mounting bolts to manufacturer specifications in a cross-pattern. Avoid over-tightening to prevent gasket damage.
7. Reconnect the throttle and choke linkages, ensuring smooth operation and correct cable tension. Verify that all connections match your reference photos.
8. Attach the fuel line securely to the carburetor inlet. Check that all fuel line clamps are tight to prevent leaks.
9. Reinstall the air intake cover and any other removed components. Double-check that all fasteners are secure.
10. Prime the fuel system by squeezing the primer bulb until firm. This ensures fuel reaches the carburetor before starting.
11. Start the engine and allow it to warm up to operating temperature. Listen for smooth idle and check for fuel leaks around all connections.
12. Adjust the idle speed and mixture screws as needed per your engine's service manual. Test throttle response and make final adjustments.

Troubleshooting & FAQ

Q: How do I confirm this carburetor fits my Mercury engine?
A: Check your engine's serial number against the compatible ranges listed in the table above (0R235168–0R833819 for 20HP, 0R235949–0R833819 and 0R558208–0R833819 for 15HP models). Verify your engine is a 4-stroke 2-cylinder configuration and that the existing carburetor serial number is 0R686020 or below.

Q: What are the signs that my carburetor needs replacement?
A: Common symptoms include rough idling, difficulty starting, poor throttle response, excessive fuel consumption, black smoke from the exhaust, or fuel leaking from the carburetor body. If cleaning and rebuilding the existing carburetor doesn't resolve these issues, replacement is recommended.

Q: Will this aftermarket carburetor perform the same as the OEM part?
A: This aftermarket carburetor is manufactured to OEM specifications and designed to deliver comparable performance and reliability. While it replaces OEM numbers 853720T15, 853720T21, and 8M0109535, minor cosmetic differences may exist, though functionality remains equivalent.

Q: Do I need to adjust the carburetor after installation?
A: Yes, most carburetors require idle speed and fuel mixture adjustments after installation to match your specific engine and operating conditions. Consult your Mercury service manual for the correct adjustment procedures and specifications.

Q: Is this an OEM or aftermarket part?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.