Sierra Bayliner Marine Ignition Switch MP39780 — Short-Mount 3-Position, 15A/30A Corrosion-Resistant

Sierra's MP39780 Bayliner marine ignition switch is a compact, three-position panel switch engineered for boats, offering a 15A ignition circuit and a 30A solenoid feed in a corrosion-resistant, short-mount housing.

This ignition switch fits a 7/8" dash hole and accommodates panels up to 5/8" thick. Built from marine-grade, glass-filled polyester with an inner seal between the cylinder and contact plate and a brass backup nut, the MP39780 prioritizes long-term electrical reliability in salty and humid environments. It uses three screw-tab terminals for simple wiring and is a conventional three-position key switch suitable for many Bayliner and similar small craft applications.

How does this switch handle marine corrosion and moisture?

The MP39780 incorporates materials and design features that reduce corrosion risk and prevent oxidation of internal contacts. Its non-conductive housing and inner seal limit water intrusion while the brass backup nut offers durable thread security where metal meets plastic.

• Marine-grade glass-filled polyester body resists saltwater corrosion.
• Inner seal between cylinder and contact plate keeps moisture away from contacts.
• Brass backup nut prevents thread corrosion and maintains panel clamping.
• Black hex face nut provides a secure, weather-resistant bezel finish.

What electrical ratings and terminal type does it use?

The switch is rated for 15 amps at 12 V DC on the ignition circuit and 30 amps at 12 V DC for the solenoid output, matching common small-boat starter and ignition loads. Wiring is straightforward thanks to three screw-tab terminals sized for secure screw or ring-lug connections.

• Rated ignition: 15 A @ 12 V DC — suitable for small outboard/inline ignition circuits.
• Rated solenoid: 30 A @ 12 V DC — powers most starter solenoids through the switch.
• Three screw-tab terminals for dependable, serviceable wiring.
• Conventional three-position key operation (off/aux/start or equivalent).

Will this fit my dash and how is it mounted?

Plan for a 7/8" mounting hole and a maximum panel thickness of 5/8" when replacing or installing this switch. The short mounting length makes it ideal where behind-dash clearance is limited; confirm your panel depth and hole size before ordering.

• Required hole size: 7/8" — standard small-dash opening for many marine switches.
• Maximum panel thickness: 5/8" for the short-mount configuration.
• Face nut is a black hex plastic for a neat, finished appearance.
• Compact length suits tight instrument panels on runabouts and small cruisers.

What practical features help with installation and serviceability?

Installation benefits include screw-tab terminals for reliable connections and a hex face nut for easy tightening from the front. The non-conductive housing reduces the chance of shorts, and the inner seal simplifies maintenance by keeping critical contact points cleaner longer.

• Three screw-tab terminals allow fast, secure wiring and straightforward troubleshooting.
• Non-conductive housing reduces grounding or shorting risks during wiring.
• Brass backup nut gives a strong clamping point behind the panel for long-term stability.
• Inner cylinder-to-plate seal lowers oxidation and contact wear.

Who is this for: The Sierra MP39780 Bayliner ignition switch is intended for boat owners, marine electricians, and DIYers seeking a compact, conventional three-position key switch with marine-grade materials and reliable electrical ratings. It's a practical replacement or upgrade for small to medium recreational craft dashboards where a short mount and corrosion resistance are priorities, and where 15A ignition and 30A solenoid capacity meet the vessel's electrical demands.