121004371A Mercury PSI Gauge | Genuine Used Part

🔧 Product Description

Genuine Mercury / Quicksilver International II Water Pressure Gauge - Listing Reference: 121004371A

A genuine used Mercury / Quicksilver mechanical water-pressure gauge with a 2-30 PSI operating range.

The black-face instrument features orange numerals, white graduations, an orange pointer and a black bezel. A mechanical pressure connection on the rear receives water pressure from the engine cooling-system takeoff, while the electrical terminals are used for gauge illumination.

The listing reference 121004371A has not been verified as a published Mercury Marine service number and may be an instrument-body, production or inventory reference. The gauge face and specification correspond with the Mercury / Quicksilver International II 2-30 PSI water-pressure gauge family.

⚙️ Key Features

• Genuine Mercury / Quicksilver marine instrument
• Mechanical 2-30 PSI water-pressure gauge
• Black face with orange numerals and pointer
• Rear mechanical pressure connection
• Electrical terminals for 12-volt illumination

🚤 Compatibility

Commonly used on

• Mercury and Mariner outboards equipped with a mechanical cooling-water pressure takeoff
• Force outboards using a compatible 2-30 PSI water-pressure system
• Mercury / Quicksilver International II-style instrument panels
• Boats using flexible pressure tubing between the engine and dashboard gauge

Typically suits

• Gauge Type: Mechanical water-pressure gauge
• Pressure Range: 2-30 PSI
• Signal Type: Direct pressure through flexible tubing
• Electrical Requirement: 12-volt supply for illumination only
• Engine Compatibility: Not restricted to one engine model; the engine must have a compatible water-pressure takeoff
• Installation Requirement: Confirm dash cutout, bezel diameter, mounting depth, tube fitting and illumination connections

🔌 Function

The gauge displays cooling-water pressure supplied from the outboard's water jacket or pressure takeoff. It helps the operator monitor water-pump performance, cooling-system restrictions and changes in water pressure while the engine is operating.

⚠️ Common Signs of Failure

• Gauge remains at zero despite verified cooling-water pressure
• Needle sticks, jumps or responds slowly
• Water leaks from the rear fitting or pressure tube
• Lens is fogged, cracked or difficult to read
• Gauge illumination no longer operates
• Low reading caused by a blocked pitot tube or pressure line rather than the gauge itself

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 79-895288Q43 → Later Mercury / Quicksilver International II 2-30 PSI water-pressure gauge kit
• 79-858654A4 → Superseded by 79-895288Q43
• 79-858654A1 → Superseded by 79-858654A4
• 79-825331A1 → Superseded by 79-858654A1

OEM / Related Numbers

• 121004371A instrument reference
• Mercury / Quicksilver: 79-825331A1
• Mercury / Quicksilver: 79-858654A1
• Mercury / Quicksilver: 79-858654A4
• Mercury / Quicksilver: 79-895288Q43
• Mercury / Quicksilver: 79-859688A2 related black-face 2-30 PSI gauge
• Mercury / Quicksilver: 79-895288A04 related black-face 2-30 PSI gauge
• Mercury / Quicksilver: 79-858654A3 related white-graduation gauge
• Mercury / Quicksilver: 79-895288Q44 related white-graduation gauge
• Mercury / Quicksilver: 79-895288A01 is a 1-15 PSI gauge and is not a direct range equivalent

Aftermarket / Verified Equivalents

• Sierra: 61238P - 2-inch 0-30 PSI mechanical water-pressure gauge kit
• Faria Beede: F12810 / OP1004 - 2-inch 0-30 PSI mechanical water-pressure gauge
• Functional replacements only; bezel style, dash cutout, mounting depth, fittings and illumination wiring must be confirmed

📦 Condition

• Genuine used part
• Removed from running engine or vessel where applicable
• In good working condition unless otherwise stated