Sierra 18-7757 Throttle Position Sensor, Flange Mount, for Mercury Racing 350/377 V-8 Marine Engines

The Sierra 18-7757 is a flange-mount throttle position sensor built for Mercury Racing 350 and 377 V-8 marine engines. It reads throttle plate position and sends a push-pull output signal to the engine control system, allowing the engine management to respond accurately to throttle input. The sensor uses a compact housing measuring 0.39 x 0.39 x 0.39 inches, making it a direct fit into the factory sensor location on applicable engine blocks.

Built to the Sierra standard for marine replacement electrical components, the 18-7757 is intended as a straightforward swap for a worn, drifting, or failed throttle position sensor. A sensor that has gone out of calibration or failed outright can cause rough idle, hesitation, stalling, or inconsistent throttle response, and replacing it with a properly matched part restores accurate throttle-to-engine communication. This sensor is application-specific, so confirming the engine model and serial number range against the fitment list below is important before ordering.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7757
• Product Type: Throttle Position Sensor
• Mounting Type: Flange Mount
• Output Type: Push-Pull
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• Weight: 0.04 pounds
• UPC: 808282294816

Fitment

• Black Scorpion SKI, 350 V-8, 1998-2002, serial range L005601 - M391599
• Black Scorpion SKI, 350 V-8, 2003-2010, serial range M391600 - W698432
• Scorpion 350 5.0L, 350 V-8, 2008-2010, serial range W698433 & UP
• 377 Scorpion MCM, 377 V-8, 1999-2005, serial range L416146 - M907201
• MX 6.2L MPI, 377 V-8, 2000-2001, serial range L680003 - M299999

Frequently Asked Questions

What engines does the Sierra 18-7757 throttle position sensor fit? The 18-7757 fits Black Scorpion SKI 350 V-8 engines (1998-2002 and 2003-2010), Scorpion 350 5.0L 350 V-8 engines (2008-2010), 377 Scorpion MCM 377 V-8 engines (1999-2005), and MX 6.2L MPI 377 V-8 engines (2000-2001).

What are the dimensions of this sensor? The Sierra 18-7757 measures 0.39 x 0.39 x 0.39 inches.

How much does the 18-7757 sensor weigh? It weighs 0.04 pounds.

How is the 18-7757 mounted? This sensor uses a flange mount, which bolts directly to the engine's throttle body location.

What kind of output signal does this sensor produce? The Sierra 18-7757 uses a push-pull output type to communicate throttle position to the engine control system.

Is the 18-7757 a genuine Sierra part? Yes, this is Sierra part number 18-7757, a marine throttle position sensor.

What is included when I order this part? One Sierra 18-7757 throttle position sensor is included.

Does the 18-7757 fit a 2008-2010 377 Mag engine? No. The 377 Mag engine for 2008-2010 uses a different sensor number; the 18-7757 covers the Black Scorpion SKI, Scorpion 350 5.0L, 377 Scorpion MCM, and MX 6.2L MPI applications listed for this part.

What serial number range applies to the Black Scorpion SKI application? For 1998-2002 model years the range is L005601 - M391599, and for 2003-2010 model years the range is M391600 - W698432.

Does the 18-7757 fit the MX 6.2L MPI DTS engine? No, the MX 6.2L MPI DTS application does not use the 18-7757 sensor; the 18-7757 is specified for the standard MX 6.2L MPI engine for 2000-2001.

What UPC identifies the Sierra 18-7757? The UPC for this throttle position sensor is 808282294816.

What serial number range applies to the Scorpion 350 5.0L application? For the 2008-2010 Scorpion 350 5.0L, the 18-7757 applies from serial number W698433 and up.