Waterproof 5-Pin Relay Kit with Flyback Diode for Boats – IP67, 12V, 40/30A NO/NC, Fused Pre-Wired Harness

Baywatt's changeover relay is a sealed IP67 waterproof relay kit with integrated flyback diode, designed for wet, vibration-exposed marine environments and modern electronic control systems. This version uses a 5-pin SPDT (NO/NC) changeover relay, rated up to 40A on the NO contact, combined with a pre-wired sealed socket, a waterproof inline fuse holder, and an integrated flyback (suppression) diode to protect sensitive control electronics.

The flyback diode suppresses the inductive voltage spike generated when the relay coil is switched OFF, preventing reverse voltage and signal backfeed into trigger wiring, switches, digital control outputs, LED drivers, and other low-current electronic interfaces.

• Marine-ready sealing: IP67 relay + sealed socket interface for spray and moisture exposure.
• Flyback diode suppression: clamps coil switch-off spikes and prevents reverse-voltage backfeed.
• Changeover logic: NO 40A (87) / NC 30A (87a) for standard ON or default-ON circuits.
• Fused battery feed included: waterproof inline fuse holder pre-installed on the power input.
• Pre-wired harness: 12 AWG power wires + 16 AWG trigger/ground wires for clean, reliable wiring.
• 5 fuses included: 20A / 25A / 30A / 35A / 40A (ATO/ATC blade format).

Integrated flyback diode (coil suppression)

This relay integrates a flyback (suppression) diode directly across the coil. Its function is to eliminate inductive voltage spikes during switch-off and prevent voltage feedback into the control circuit. This protection is required when the relay is driven by modern electronic outputs or LED control equipment.

• Electronic switch panels and push buttons
• Digital controllers, ECUs, and logic outputs
• LED lighting drivers, dimmers, and control modules
• CAN / NMEA or other low-current signal outputs

By suppressing coil backfeed, the integrated diode protects sensitive electronics, improves system reliability, and stabilizes electronically controlled and LED-based installations.

Typical marine uses

Use this relay when a low-current control (helm panel, push button, controller output) must drive a moderate-current load with proper protection and without exposing the control circuit to inductive feedback.

• Deck, spreader, and navigation lighting
• Horn or signal devices
• Washdown, livewell, and accessory pumps
• Blowers and ventilation fans
• Accessory power switching from electronic control panels

NO / NC – Changeover behavior

• 87 (NO – Normally Open, 40A): OFF by default, turns ON when the relay coil is energized.
• 87a (NC – Normally Closed, 30A): ON by default, turns OFF when the relay coil is energized.

NO supports standard “turn ON when triggered” circuits. NC supports default-ON or fail-safe logic where the load is powered when the relay is not energized.

Pinout & wire colors (RW1240-D)

Polarity required (flyback diode): apply +12V to pin 86 to energize the coil and connect pin 85 to battery negative. Reversed polarity will prevent correct operation and may damage the suppression diode.

What’s included

• 1× IP67 sealed 5-pin relay with integrated flyback diode (SPDT changeover, NO/NC)
• 1× sealed socket with pre-wired harness
• 1× waterproof inline fuse holder (pre-installed on the battery feed)
• 5× blade fuses: 20A / 25A / 30A / 35A / 40A
• Mounting bracket

Installation notes (marine wiring)

• Respect coil polarity (pins 85/86) due to the integrated flyback diode.
• Select the fuse value based on the device current and cable sizing.
• Keep the fused feed (pin 30) as close to the power source as practical.
• Use adhesive-lined heat-shrink connectors for moisture resistance.
• If unused, insulate pin 87a (NC) individually.