Check Valve Kit – Fits Mercury/Mariner 35/50/60 HP Outboard Motors (Replaces 21-13424A1)

$35.99 $57.00

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Product Details

This aftermarket Check Valve Kit is designed for Mercury and Mariner 35, 50, and 60 HP 2-cylinder and 3-cylinder outboard engines, primarily from 1980s and 1990s model years. It serves as a crucial component in the fuel system to ensure proper fuel flow and prevent backflow, maintaining engine performance and reliability.

It is a direct replacement for Mercury/Mariner OEM part numbers 21-13424A1 and 8M0084275, as well as GLM part GLM40170.

Installation: Installs as a fuel system component.
Fuel Compatibility: Designed for use with gasoline.
Warranty: Backed by a 30-day warranty provided by Green Bay Prop.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number	Superseded By
Mercury/Mariner	21-13424A1	8M0084275
GLM	GLM40170

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury and Mariner models, compatibility is determined by serial number range. Please verify your engine's serial number falls within the ranges listed for your specific model and horsepower.

Brand	Model	Rated HP	Stroke	Years / S/N Range	OEM Part No.	Notes
Mercury	2-cylinder	35	2-Stroke	From S/N 209608 & Up	21-13424A1	Superseded by 8M0084275
Mercury	2-cylinder	35	2-Stroke	S/N 6445653 thru 0B110788	21-13424A1	Superseded by 8M0084275
Mercury	2-cylinder	35	2-Stroke	S/N 9384476 & Up	21-13424A1	Superseded by 8M0084275
Mariner	3-cylinder	50	2-Stroke	S/N 6428681 thru 0B122929	21-13424A1	Superseded by 8M0084275
Mercury	3-cylinder	50	2-Stroke	S/N 6428681 thru 0B122929	21-13424A1	Superseded by 8M0084275
Mariner	3-cylinder	50	2-Stroke	S/N 7208333 thru 0A721307	21-13424A1	Superseded by 8M0084275
Mercury	3-cylinder	50	2-Stroke	S/N 7208333 thru 0A721307	21-13424A1	Superseded by 8M0084275
Mariner	3-cylinder	50	2-Stroke	S/N 9385911 thru 9469199	21-13424A1	Superseded by 8M0084275
Mercury	3-cylinder	50	2-Stroke	S/N 9385911 thru 9469199	21-13424A1	Superseded by 8M0084275
Mariner	3-cylinder	60	2-Stroke	S/N 6428681 thru 0B122929	21-13424A1	Superseded by 8M0084275
Mercury	3-cylinder	60	2-Stroke	S/N 6428681 thru 0B122929	21-13424A1	Superseded by 8M0084275
Mariner	3-cylinder	60	2-Stroke	S/N 7208333 thru 0A721307	21-13424A1	Superseded by 8M0084275
Mercury	3-cylinder	60	2-Stroke	S/N 7208333 thru 0A721307	21-13424A1	Superseded by 8M0084275
Mariner	3-cylinder	60	2-Stroke	S/N 9385911 thru 9469199	21-13424A1	Superseded by 8M0084275
Mercury	3-cylinder	60	2-Stroke	S/N 9385911 thru 9469199	21-13424A1	Superseded by 8M0084275

Technical Specs

Product Type: Check Valve Kit
Installation: Fuel System Component
Fuel Type: Gasoline
Dimensions: 11.5″ L x 10.2″ W x 2.0″ H
Warranty: 30 days (Green Bay Prop)
Other Technical Attributes: Original packaging (varies by retailer)

What’s in the Box

1 x Check Valve Kit (Replaces 21-13424A1)

Installation Notes

Ensure the engine is off and the battery is disconnected. Relieve all pressure from the fuel system according to your service manual's procedure.
Place absorbent shop towels around the fuel components to catch any spilled fuel.
Carefully locate and disconnect the fuel lines leading to and from the old check valve assembly.
Remove the mounting hardware securing the old check valve and remove it from the engine.
Install the new check valve from the kit, ensuring all seals and gaskets are correctly seated. Secure it with the original mounting hardware.
Reconnect the fuel lines to the new valve, ensuring connections are tight and secure.
Prime the fuel system as per your engine's specifications and carefully check for any leaks around the new installation.
Once no leaks are detected, reconnect the battery, start the engine, and check again for leaks while it is running.

Troubleshooting & FAQ

How do I confirm this kit fits my specific engine?

The most reliable method is to match your engine's serial number to the ranges listed in the compatibility table. While the kit fits many 35-60 HP Mercury and Mariner models, serial number is the final check for older engines.

What are common symptoms of a failing check valve?

A faulty check valve can cause issues like difficulty starting, poor idling, stalling, a loss of power, or fuel failing to stay in the lines (loss of prime). It may also allow fuel to flow back into the tank, making the primer bulb difficult to firm up.

What is the difference between OEM part 21-13424A1 and 8M0084275?

The part number 8M0084275 is the official superseded (updated) part number from Mercury for the original 21-13424A1. They are functionally identical, and this aftermarket kit is designed to replace both versions.

Can I install this kit myself?

If you are experienced with marine fuel systems and have the correct tools, you can perform the installation. However, due to the fire risk associated with working on fuel systems, we recommend professional installation for safety and to ensure a leak-free result.

Is any special maintenance required for the new check valve?

No special maintenance is needed for the valve itself. However, regular inspection of all fuel lines and connections for signs of wear, cracking, or leaks is a critical part of routine engine maintenance.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

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