Sierra MP39090 Marine Ignition Starter Switch – 3-Position, Magneto, 6-Screw, 12V/15A
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Sierra MP39090 Marine Ignition Starter Switch – 3-Position Magneto, 6-Screw Terminal, 12V/15A
The Sierra MP39090 is a heavy-duty marine ignition starter switch built for magneto ignition systems with complex wiring configurations. The 6-screw terminal layout accommodates engines that require additional circuit connections beyond a standard magneto switch — such as dual-circuit magneto systems or setups with separately wired choke or accessory circuits. A corrosion-resistant polyester housing with an inner cylinder seal keeps moisture out and eliminates the risk of shorts, making it a reliable choice for saltwater and high-humidity marine environments.
The 3-position action — Off, Ignition, and Start — provides clean, positive control over engine startup and shutdown, backed by a 30A solenoid rating. The 1-1/8" cylinder diameter and 7/8" mounting hole fit a wide range of marine dash panels.
Key Specifications
- Part Number: 11-MP39090
- Switch Type: 3-Position (Off – Ignition – Start)
- Ignition Type: Magneto
- Voltage: 12V DC
- Current Rating: 15A
- Solenoid: 30A
- Cylinder Diameter: 1-1/8"
- Mounting Hole: 7/8"
- Terminals: 6 Screw
- Housing Material: Polyester (corrosion-resistant)
- Inner Cylinder Seal: Yes
Compatible Applications
- Outboard and inboard engines with magneto ignition systems requiring 6-terminal wiring
- Dual-circuit magneto systems or engines with separately wired choke or accessory circuits
- Marine helm panels with a 7/8" mounting hole accepting a 1-1/8" cylinder switch
- 12V DC electrical systems requiring a 3-position Off/Ignition/Start switch
- Direct replacement for worn or damaged OEM 6-screw magneto ignition switches
Parts Desk Insights
The MP39090 is the right choice when your magneto ignition engine has a wiring harness that requires 6 screw terminals — more connection points than the standard 5-screw switches in this family. If your engine only needs 5 terminals, the Sierra MP39100 Magneto 5-Screw Polyester Switch is the simpler and slightly lower-cost option. For a compact 5/8" cylinder magneto switch with push-to-choke, the Sierra MP39760 Magneto Polyester Switch covers that application. If a brass-bodied magneto switch is preferred, the Sierra MP39040 Brass Magneto Switch is available, though rated at 10A. For a conventional ignition system instead of magneto, the Sierra MP39770 Conventional Polyester Switch is the correct fit.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.