Ignition Key Switch – Fits Mercury/Mariner DFI, EFI & MPI Outboard Motors (Replaces 87-17009A5)

Ignition Key Switch – Fits Mercury/Mariner DFI, EFI & MPI Outboard Motors (Replaces 87-17009A5)

This panel-mounted ignition key switch is a reliable replacement for Mercury and Mariner outboard motor control boxes requiring a 6-wire connection. It is designed for compatibility with a range of DFI (Direct Fuel Injection), EFI (Electronic Fuel Injection), and MPI (Multi-Point Injection) engines.

This unit is a direct replacement for Mercury part numbers 87-17009A5 and 87-17009A2, as well as Sierra part numbers MP41070-2, MP41070-1, and MP41070.

• Installation Type: Panel Mount
• Connection: 6-Wire
• Package Includes: 1x Ignition Key Switch, 2x Keys

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 × Ignition Key Switch (87-17009A5)
• 2 × Ignition Keys

Installation Guide

1. Safety First: Disconnect the boat's battery cables (negative first, then positive) to prevent electrical shorts.
2. Access the Switch: Open or remove the control box panel to access the back of the old ignition switch.
3. Label and Disconnect: Before disconnecting, label each wire to ensure correct placement on the new switch. Carefully unplug the 6-wire connector.
4. Remove Old Switch: Unscrew the mounting nut on the front of the panel and remove the old ignition switch.
5. Install New Switch: Insert the new ignition switch into the panel, orient it correctly, and tighten the mounting nut until snug. Do not overtighten.
6. Reconnect Wires: Attach the 6-wire connector to the new switch, ensuring it is fully seated and secure.
7. Test the System: Reconnect the battery (positive first, then negative) and test all switch positions (OFF, RUN, START) to confirm proper function before heading out on the water.

Troubleshooting & FAQ

Q: How do I confirm this ignition switch fits my specific Mercury engine?

A: This switch fits various Mercury/Mariner DFI, EFI, and MPI outboard motors. The best way to confirm is to match your existing part number to the ones listed in our cross-reference table (87-17009A5, 87-17009A2) or the Sierra equivalents. Also, ensure your system uses a 6-wire connection.

Q: What are the common signs that my ignition key switch is failing?

A: Common symptoms include difficulty turning the key, the engine not cranking or starting intermittently, the engine shutting off unexpectedly, or a loss of power to accessories when the key is in the 'RUN' position. Corrosion on the contacts can also be a visual indicator.

Q: Is this a direct replacement for the Sierra MP41070-2?

A: Yes, this ignition switch serves as a direct aftermarket replacement for Sierra part numbers MP41070-2, MP41070-1, and MP41070, along with the OEM Mercury numbers.

Q: OEM vs. Aftermarket?

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.