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

The Sierra MP39780 Bayliner marine ignition switch is a compact, corrosion-resistant 3-position replacement switch rated for 15A ignition and 30A solenoid at 12V, built to fit a 7/8" panel hole and short panel thicknesses up to 5/8".

This ignition switch is designed for Bayliner and other boats that need a reliable, direct-replacement control for starting and accessory power. Molded from marine-grade glass-filled polyester with internal sealing and brass hardware, it resists corrosion and electrical shorts while offering standard 3-screw tab connections for straightforward wiring. Its short-profile design suits consoles or dash panels with limited depth.

Will this ignition switch fit my Bayliner dash or panel?

The switch fits panels drilled for a 7/8" hole and accepts a maximum panel thickness of 5/8" due to its short-length design. Confirm your panel's hole diameter and thickness before ordering to ensure a correct fit.

• Hole size: 7/8" (standard Bayliner dash opening)
• Maximum panel thickness: 5/8" (short profile version)
• Face nut: hex black plastic for a secure, trimmed finish
• Back up nut: brass for corrosion-resistant fastening

How durable is the switch in saltwater and humid conditions?

This model uses marine-grade glass-filled polyester housing and an inner seal between the cylinder and contact plate to minimize moisture ingress. Non-conductive housing reduces the risk of shorts and brass fastening components resist rust, making it suitable for typical recreational boating environments.

• Material: marine-grade glass-filled polyester for strength and weather resistance
• Inner seal: prevents corrosion at the lock-contact interface
• Back up nut brass: improves long-term corrosion protection
• Non-conductive housing: reduces electrical short potential

What electrical ratings and terminal type does it use?

The switch provides a rated ignition circuit of 15 amps at 12 volts DC and a 30-amp solenoid rating at 12 volts DC, matching many small-boat starting systems. It uses three screw-tab terminals so you can connect standard wiring harnesses without crimp-only terminals.

• Ignition rating: 15 Amp @ 12V DC
• Solenoid rating: 30 Amp @ 12V DC
• Terminal type: 3 screw tab for secure wiring
• Type: 3-position conventional (OFF/ACCESSORY/START style operation)

Who is this switch for? The Sierra MP39780 is aimed at boat owners, marine technicians, and DIYers needing a compact, corrosion-conscious replacement ignition switch for Bayliner boats or other vessels using the same mounting and electrical specs. If you require a short-profile unit with sealed internals, brass backup nut, and non-conductive housing to reduce shorts, this switch is a practical, cost-effective option. Always verify hole size, panel thickness, and amperage compatibility with your vessel's wiring before installation.