Starter Solenoid Relay for Mercury 9.9HP, 15HP, 30HP, 40HP, 50HP, 60HP, 75HP & 90HP 4-Stroke Outboards – Replaces 89-825096T, 825096T01 & Sierra 18-5821

Product Details

This Starter Solenoid Relay is an aftermarket replacement for selected Mercury 4-stroke outboard electrical systems. It is listed for Mercury 9.9HP, 15HP, 30HP, 40HP, 50HP, 60HP, 75HP and 90HP applications, with fitment depending on the engine model and serial-number range.

Use this starter solenoid to replace the listed Mercury reference numbers and Sierra aftermarket reference. Always compare the original component, terminal arrangement and engine identification before ordering.

• Replacement starter solenoid relay for selected Mercury 4-stroke outboards
• Designed for direct replacement where the original component and terminals match
• Applicable to specified Mercury 9.9HP through 90HP 4-stroke applications
• Aftermarket replacement component; not an OEM Mercury part

Part Number Matrix

Use these references to compare the replacement with your original part.

Engine & Model Compatibility

The following applications are identified for the corresponding starter solenoid reference. Year ranges are shown as reported in the catalog and may still require serial-number verification.

Technical Specs

Component type

Starter solenoid relay

Application

Selected Mercury 4-stroke outboard electrical systems

Installation

Direct replacement where the original part and terminal configuration match

Reference numbers

89-825096T, 825096T01 and Sierra 18-5821

What's in the Box

• 1 × Starter solenoid relay

Installation Notes

1. Disconnect the negative battery cable before beginning work on the starting circuit.
2. Locate the existing starter solenoid relay on the outboard.
3. Photograph or label the wiring before removing the old component.
4. Disconnect the electrical terminals and remove the original mounting hardware.
5. Compare the replacement terminals, mounting arrangement and overall configuration with the original.
6. Install the replacement relay using the original or equivalent hardware.
7. Reconnect each wire to its original terminal and make sure all connections are clean and tight.
8. Reconnect the negative battery cable and test starter operation.

Troubleshooting & FAQ

How do I know if my starter solenoid relay is failing?

Common symptoms include a clicking sound when the key is turned without engine cranking, intermittent starting, or no starter engagement. Loose, corroded or damaged wiring can cause similar symptoms, so inspect the battery, cables and terminals before replacing the relay.

Is this compatible with 2-stroke Mercury engines?

This listing is intended for the specified Mercury 4-stroke applications. Do not assume compatibility with a 2-stroke engine based only on horsepower. Verify the engine model, stroke type, serial number and original solenoid configuration.

Which Mercury applications are listed for this relay?

The catalog fitment covers Mercury 9.9HP and 15HP 4-stroke engines from 1999 and newer, 30HP from 2002 and newer, 40HP, 50HP and 60HP from 2001 and newer, and 75HP and 90HP from 2000 and newer. Specific model and serial-number restrictions may apply.

Will this work if my original part number is slightly different?

Fitment is identified for Mercury 89-825096T and 825096T01, with Sierra reference 18-5821. A different number is not automatically interchangeable. Compare the original part and consult the engine parts catalog before ordering.

Can I install this myself or do I need a mechanic?

Installation may be straightforward for someone familiar with marine electrical systems. Disconnect the battery first and carefully document the wiring. Professional installation is recommended if the terminal layout, wiring or engine application is uncertain.

What causes starter relay failure on outboards?

Moisture, salt exposure, vibration, corrosion, worn contacts and loose electrical connections can affect starter solenoid performance. Inspect the terminals and wiring regularly and correct corrosion or poor connections before installing a replacement.

How does this compare to the OEM Mercury relay?

This is an aftermarket replacement, not an OEM Mercury component. It is intended to replace the listed reference numbers when the engine application and physical configuration match.

OEM vs. aftermarket?

This listing is for an aftermarket replacement. It is not manufactured or sold by Mercury Marine.

Shipping speed & cost

We ship worldwide quickly—typical transit is 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 an issue arises, contact support with your order details. Returns are accepted within our standard window when the item is unused and in its original condition. See the applicable policy page or contact support for instructions.

Safety & Important Info

• Verify the engine model, stroke type, serial number, original part number and terminal arrangement before ordering.
• Compare the replacement with the original component before installation.
• Disconnect the battery before servicing the starter circuit.
• This is an aftermarket replacement, not an OEM Mercury component.
• Professional installation is recommended when wiring or fitment is uncertain.

About Sea Sierra

• Pro-Grade Standards — We supply marine replacement parts selected for practical service applications.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing for replacement marine components.