MerCruiser® 864856A1 MAP Sensor
MerCruiser® 864856A1 MAP Sensor
Mercury superseded 805217A1 to current service number 864856A1.
This is a MAP (Manifold Absolute Pressure) sensor — it measures manifold pressure only. The ECM uses this signal as one input in determining engine operating conditions and fuel/ignition strategy. Do not confuse with the MAPT sensor (885165 / 8M0087834) used in ECM-555 applications, which combines pressure and temperature sensing in a single unit.
864856A1 is the current Mercury service number. If your existing sensor is labeled 805217A1, that number was superseded to 864856A1. Both numbers refer to the same current MAP sensor assembly.
864856A1 is the current Mercury/MerCruiser service number for the Manifold Absolute Pressure (MAP) sensor used across the 454 MAG EFI/MPI, 7.4L MPI, 7.4LX MPI, 350 Magnum MPI, 502 Magnum MPI, MX 6.2L MPI, and 8.2L MPI MIE engine families. It supersedes the earlier OEM number 805217A1, which is no longer the active service number.
The MAP sensor reports intake-manifold absolute pressure information to the engine control module (ECM). The ECM uses this signal as one input when determining engine load, operating conditions, and fuel/ignition strategy. A MAP sensor does not measure temperature — it measures pressure only.
MAP-related symptoms can overlap with vacuum leaks, wiring faults, connector problems, fuel-delivery problems, and other engine-management faults. Symptoms alone do not establish a failed MAP sensor. Proper diagnosis using the appropriate service documentation is required before replacing this component.
Verify your exact engine model, serial number, and existing OEM part number against the application table below before ordering. This sensor is not interchangeable with the MAPT sensor (885165 / 8M0087834) used in ECM-555 applications, nor with the MAP sensor (861249A1 / 8M0186195) used in the 4.3L EFI, 5.0L EFI, 7.4L L29, 496 Mag, and 8.1L MIE families.
This MAP sensor applies to the 454 MAG EFI/MPI, 7.4L MPI, 7.4LX MPI, 350 Magnum MPI, 502 Magnum MPI, MX 6.2L MPI, and 8.2L MPI MIE engine families. It is NOT the correct sensor for the 4.3L/5.0L EFI or 7.4L L29 families (those use 861249A1 / 8M0186195), and NOT the correct sensor for ECM-555 applications (those use MAPT 885165 / 8M0087834). Verify your exact engine model, serial number, and existing OEM part number before ordering.
Aftermarket cross-reference: Sierra 18-7684 (aftermarket — not a Mercury/MerCruiser OEM number). Verify fitment independently before ordering any aftermarket part.
Verified Engine Applications
Application relationships are verified against Mercury Marine primary source documentation.
Customers Replacing This Part Also Consider
Related components are shown only for verified engine/application matches.
MerCruiser® 454 MAG EFI — 454 V8 — 1994–1996
MerCruiser® 454 MAG EFI Ski — 454 V8 — 1994–1996
MerCruiser® 454 MAG EFI Ski — 454 V8 — 1996–1997
MerCruiser® 454 MAG MPI — 454 V8 — 1996–1997
MerCruiser® 454 MAG MPI — 454 V8 — 1997–1998
MerCruiser® 454 MAG MPI Horizon MIE — 454 V8 — 1998
MerCruiser® 7.4L MPI MIE — 454 V8 — 1995–1996
MerCruiser® 7.4L MPI MIE — 454 V8 — 1997
MerCruiser® 7.4LX MPI — 454 V8 — 1996
MerCruiser® 7.4LX MPI — 454 V8 — 1997
MerCruiser® 454 MAG MPI — 454 V8 — 1999–2001
MerCruiser® 454 MAG MPI Horizon MIE — 454 V8 — 1999–2001
MerCruiser® 350 MAG MPI — 350 V8 — 1999
MerCruiser® 350 MAG MPI — 350 V8 — 1999–2001
MerCruiser® 350 MAG MPI Horizon MIE — 350 V8 — 1999–2001
MerCruiser® 350 MAG MPI MIE — 350 V8 — 1999–2001
MerCruiser® 350 MAG MPI Ski — 350 V8 — 1999–2001
MerCruiser® 502 Magnum MPI — 502 V8 — 1993–1996
MerCruiser® 502 Magnum MPI — 502 V8 — 1997–1998
MerCruiser® 502 Magnum MPI — 502 V8 — 1999–2001
MerCruiser® MX 6.2L MPI — 377 V8 — 2000–2001
MerCruiser® 8.2L MPI MIE — 502 V8 — 1996
MerCruiser® 8.2L MPI MIE — 502 V8 — 1997–1998
MerCruiser® 8.2L MPI MIE — 502 V8 — 1999–2001