79-816857A-1 Mercury Fuel Gauge | Genuine Used Part

🔧 Product Description

Genuine Mercury Quicksilver QSI Fuel Level Gauge - Part Number: 79-816857A1

A genuine used Mercury Quicksilver QSI analog fuel-level gauge for conventional 12-volt marine fuel-tank sender systems.

This legacy gauge displays tank level from EMPTY to FULL using the matching resistance sender. Sender range, ground quality and wiring polarity must be confirmed before installation.

⚙️ Key Features

• Genuine Mercury Quicksilver OEM QSI fuel gauge
• Correct Mercury part number 79-816857A1
• Analog EMPTY-to-FULL fuel-level display
• Designed for conventional 12-volt marine instrumentation
• Suitable for standard US-type 240-33 ohm senders when calibration matches

🚤 Compatibility

Commonly used on

• Mercury, Mariner and MerCruiser 12-volt helm instrumentation
• Marine fuel tanks fitted with a compatible 240-33 ohm sender

Typically suits

• Engine models:
• Mercury and Mariner outboard-powered boats using a stand-alone analog fuel sender
• MerCruiser sterndrive and inboard boats using a stand-alone analog fuel sender
• Single-tank 12-volt marine installations with FULL approximately 33 ohms and EMPTY approximately 240 ohms
• HP Range: Not engine-specific
• Engine Type: 12-volt marine fuel-level instrumentation
• Year Range: Approximately late 1980s - 1990s

🔌 Function

The gauge measures resistance through the tank sender and converts it into an approximate fuel-level reading. It requires a sound sender ground, correct sender resistance and stable instrument power.

⚠️ Common Signs of Failure

• Gauge remains on EMPTY or FULL
• Needle changes sharply when the boat moves
• Reading is inaccurate because the sender range is mismatched
• Corroded sender or ground wiring causes intermittent operation
• Internal gauge movement or illumination fails

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 79-816857A1 current known OEM service reference
• 816857A1 original unprefixed Mercury reference

OEM / Related Numbers

• 79-816857A1
• 79-816857A-1
• 79816857A1
• 816857A1
• Mercury QSI fuel-level instrument

Aftermarket / Verified Equivalents

• Sierra: 57902P - Amega 240-33 ohm fuel gauge
• Veethree: 57902E - Amega 240-33 ohm fuel gauge
• ECMS: 800-00129 - 240-33 ohm marine fuel gauge

📦 Condition

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