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Marshall

Marshall Tachometer Filter Ignition Noise Reduction

★★★★★4.2 (14 reviews)

Marshall Tachometer Filter eliminates ignition noise and signal surges for clean, steady tachometer readings.

$39.95*
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*Price sourced from Amazon.com. Last updated:Jul 14, 2026.Price and availability are subject to change.

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Overview

The Marshall Instruments Tachometer Filter is a compact inline device engineered to clean up the electrical signal between your ignition system and tachometer. Ignition systems — particularly those with high-energy coils, aftermarket ignition boxes, or multiple spark discharge setups — can produce voltage spikes and radio frequency noise that cause tachometer needles to bounce, flutter, or display inaccurate RPM readings. This filter absorbs those surges and smooths the signal before it reaches the tachometer, resulting in a steady, reliable readout.

Measuring just 2 inches wide, 0.75 inches high, and 1 inch deep, the filter is small enough to mount virtually anywhere in the engine bay or behind the dashboard. It serves as a direct drop-in replacement for original GM tachometer filters and is universally compatible with a wide variety of aftermarket and factory tachometers. Installation requires only basic wiring — the filter connects inline between the ignition signal wire and the tachometer input — with no cutting, splicing, or special tools beyond standard electrical connectors.

Key Features

compact, easy to install, tachometer filter

Specifications

Brand
Marshall
Product
Tachometer Filter
Function
Eliminates Signal Noise and Surges
Compatibility
Universal / Direct GM Replacement
Width
2"
Height
0.75"
Depth
1"

Pros & Cons

👍 Pros

  • Eliminates needle bounce and erratic readings caused by ignition signal noise.
  • Compact size at 2" x 0.75" x 1" fits easily in tight engine bay spaces.
  • Universal compatibility works with a wide range of tachometers and ignition systems.
  • Simple inline wiring installation requires no specialized tools or modifications.
  • Direct replacement for original GM tachometer filters for straightforward swaps.

👎 Cons

  • Very limited product documentation with no detailed installation instructions included.
  • Only addresses signal noise — will not fix tachometer issues caused by faulty wiring or bad grounds.
  • No shielded housing, which may limit effectiveness in extremely high-interference environments.
  • Generic appearance with no markings, making it hard to identify once installed.

Frequently Asked Questions

It filters out electrical noise and voltage surges from the ignition system that can cause tachometer needles to bounce, flutter, or read inaccurately, resulting in a smooth and stable RPM display.
Yes, the filter is universally compatible and works with most aftermarket and OEM tachometers that receive signal from the ignition system.
Yes, it is designed as a direct replacement for original GM tachometer filters and fits the same wiring configuration.
Installation is straightforward — the filter is compact at 2 inches wide by 0.75 inches high by 1 inch deep and wires inline between the ignition signal source and the tachometer.

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