Sierra marine ignition switch MP41040 — 4-position conventional, 15A 12V, black knurled face

The Sierra MP41040 is a four-position conventional marine ignition switch designed as a universal-fit replacement for boats and high-horsepower engines.

Built to withstand saltwater exposure and demanding engine environments, this Sierra ignition switch replaces many original equipment units while meeting or exceeding OE specifications. It offers a compact footprint, brass backup nut, knurled black plastic face nut, and screw-tab terminals engineered for reliable electrical connection at 15 amps and 12 VDC. The MP41040 is supplied by Sierra, a trusted OEM parts vendor, and is backed by the brand’s industry-leading warranty covering parts and many service-related costs.

How will this ignition switch fit my boat’s dashboard?

The MP41040 is made as a universal-fit component to simplify replacements in a wide range of panels and dash layouts. With a 7/8" mounting hole requirement and a short shaft length that accommodates up to 1-1/8" panel thickness, it installs easily into most recreational and commercial craft.

• Mounting hole: 7/8" diameter
• Maximum panel thickness: 1-1/8"
• Face nut: knurled black plastic for secure hand tightening
• Backup nut: brass for corrosion resistance

What electrical connections and ratings does the switch provide?

This ignition switch uses four screw-tab terminals that accept standard wire sizes for marine electrical systems, making wiring straightforward for most installations. It is rated for 15 amps at 12 VDC, appropriate for typical ignition circuits and compatible accessories when installed per manufacturer guidance.

• Terminal type: 4 screw tab for reliable fastening
• Electrical rating: 15 Amp @ 12 VDC
• Conventional 4-position operation for off, accessory, on, start configurations
• Designed for standard ignition wiring practices

Why choose Sierra MP41040 over other aftermarket switches?

Sierra manufactures parts to satisfy the tougher demands of high-horsepower marine engines and corrosive environments, and this switch is no exception. The MP41040 is engineered to meet or exceed the original equipment it replaces, and Sierra supports it with a warranty that can cover shop labor, haul-out, towing fees, and related incidental charges when applicable.

• Meets or exceeds original equipment specifications
• Materials: brass backup nut and durable plastic face nut for longevity
• Trusted OEM supplier to many engine makers and boat builders
• Industry-leading warranty with specific service coverage details

How difficult is installation and what do I need to know before buying?

Installation is generally straightforward for anyone comfortable with basic dash wiring and panel work; the screw-tab terminals simplify electrical connections and the knurled face nut allows tool-free panel tightening in most cases. Confirm the 7/8" hole size and panel thickness compatibility before purchase and follow electrical safety practices, including disconnecting the battery and using proper wire gauges and connectors.

• Confirm panel hole: 7/8" required
• Check panel thickness: up to 1-1/8" supported
• Use correct wire gauge and clean screw-tab connections
• Disconnect battery and follow marine electrical safety steps during install

Who is this for: The Sierra MP41040 ignition switch is ideal for boat owners, marine technicians, and DIY installers who need a reliable, corrosion-resistant replacement for a conventional four-position ignition. It suits a range of recreational and light commercial vessels, especially where OE-level durability and an OEM-grade warranty are priorities.