Sierra Insulator Blocks 18-99519, Replaces Mercury CDI Electronics 994-3981, 2-Pack

The Sierra 18-99519 Insulator Blocks are a 2-pack replacement component used in marine ignition systems, designed as an equivalent to the Mercury CDI Electronics 994-3981 insulator block. Insulator blocks mount ignition components such as coils or switch boxes while electrically isolating them from the engine mounting surface, protecting sensitive ignition circuitry from stray current and vibration-related wear. Each block uses a screw-type connector for secure installation.

Sold as a pack of two, these insulator blocks are a lightweight, low-cost part to keep on hand for ignition system maintenance or repair. Because they are designed to match the Mercury CDI Electronics 994-3981 insulator block, they can be used as a direct equivalent when servicing compatible ignition setups.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99519
• Package Quantity: 2 per pack
• Connector Type: Screw
• Weight: 0.04 pounds

Fitment

Fits ignition systems using the Mercury CDI Electronics 994-3981 insulator block.

Replaces (OEM)

• Mercury CDI Electronics 994-3981

Frequently Asked Questions

What is the Sierra 18-99519 insulator block used for? The Sierra 18-99519 insulator block mounts and electrically isolates ignition components, such as coils or switch boxes, from the engine mounting surface in a marine ignition system.

How many insulator blocks come in this package? The Sierra 18-99519 is sold as a 2-pack, giving you two insulator blocks per package.

Does the Sierra 18-99519 replace the Mercury CDI Electronics 994-3981 insulator block? Yes, the Sierra 18-99519 is designed as an equivalent to the Mercury CDI Electronics 994-3981 insulator block.

What type of connector does this insulator block use? This insulator block uses a screw-type connector for mounting and installation.

How much does the Sierra 18-99519 insulator block weigh? Each package of the Sierra 18-99519 insulator blocks weighs 0.04 pounds.

Is the Sierra 18-99519 an OEM or aftermarket part? The Sierra 18-99519 is an aftermarket insulator block manufactured to match the Mercury CDI Electronics 994-3981 part for compatible ignition system repairs.

Can I use the Sierra 18-99519 to replace just one damaged insulator block? Since the Sierra 18-99519 comes as a 2-pack, you will have a spare block on hand even if you only need to replace one damaged unit.

What ignition components typically use this insulator block? Insulator blocks like the Sierra 18-99519 are typically used to mount ignition coils or switch boxes while isolating them from the engine mounting surface.

Is installation of the Sierra 18-99519 straightforward? Yes, the Sierra 18-99519 uses a simple screw connector, making it straightforward to install in place of the original insulator block.

What is included when I order the Sierra 18-99519? An order of the Sierra 18-99519 includes two insulator blocks (a 2-pack).