Overview

The Hella Marine 933332011 is a 12V mini ISO SPDT (Form C) relay with a mounting bracket for switching higher-current circuits from a low-current control. It is rated for 40A continuous on the normally open contact and 20A continuous on the normally closed contact (at 85 C), using a standard 5-terminal layout.

On a boat, this is commonly used to keep heavy current out of the helm switch or controller and place the switching closer to the load, such as deck and spreader lights. The relay body is IP54-rated, so it tolerates spray and dust when installed in a protected location, but it is not meant for direct exposure on deck or in the bilge.

Key features

• 12V DC coil for standard 12V onboard electrical systems
• SPDT (1 Form C) switching with 5 terminals (30, 87, 87a, 85, 86)
• 40A continuous rating on N/O and 20A continuous on N/C (at 85 C)
• Mini ISO plug-in format with 6.3 mm x 0.8 mm blade terminals
• Mounting bracket for fastening to a bulkhead or electrical panel
• IP54-rated housing for protected installations where spray and dust are possible
• Handles inrush loads up to 150A, useful for circuits that hit hard at switch-on

Compatibility and fit

This relay fits the common mini ISO footprint used in many marine and vehicle electrical systems, including standard 5-terminal relay sockets and harnesses built for 6.3 mm blade terminals. It is intended for 12V systems; for 24V vessels, the correct approach is a 24V-coil relay rather than dropping voltage with resistors.

Installation and wiring

Mount it using the bracket in a dry, serviceable area such as inside a console, under the dash, in a locker, or in a protected engine-room electrical panel. Typical wiring is 85/86 for the coil, 30 as the common feed, 87 as normally open output, and 87a as normally closed output. Protect the supply to terminal 30 with a properly sized fuse or breaker placed close to the source, and use wire gauge appropriate for the load current and run length.

Electrical notes for marine systems

This relay does not include built-in coil suppression, so if you are triggering it from sensitive electronics, external suppression may help reduce switching noise. If you are switching inductive loads, confirm that the circuit protection and wiring are appropriate for both steady current and switch-on inrush.

Use cases on board

It is a good match for boats that run deck, spreader, or work lights from a small helm switch, keypad, or low-current controller output, while keeping the high-current path short and out of the dash. It also works well in refits where you are adding new lighting or accessories and want clean, serviceable switching in an electrical panel.

Maintenance and care

Periodically check terminals for looseness and heat discoloration, especially on high-current lighting circuits. In humid or salt-prone areas, corrosion control on the terminals and keeping the relay in a covered location goes a long way toward long-term reliability.