The Mercury Racing EFI Air Temperature Sensor Adapter, OEM part number 816885, is a genuine Mercury Racing / Quicksilver component used on several of Mercury Racing's most recognizable 2.5-liter EFI two-stroke outboards, including the 260 EFI, 280 ROS, 260 Offshore, 280 Short Shaft, 300 Drag, and F1 S3000.
Installed in the intake air temperature sensing system, this adapter provides the proper mounting interface and seal for the EFI air temperature sensor. While small in size, it plays an important role in ensuring the sensor is correctly positioned and secured so the ECU can receive accurate intake air temperature information.
Why Air Temperature Matters
Mercury Racing EFI systems continuously monitor intake air temperature because air density changes as temperature changes. Cooler air is denser and contains more oxygen, while warmer air is less dense. The ECU uses this information as part of its fuel delivery calculations to help maintain consistent engine performance across varying weather and operating conditions.
Accurate sensor data contributes to proper fuel metering, clean throttle response, consistent idle quality, and reliable engine operation throughout the RPM range. Because of this, the condition of the sensor adapter and its sealing O-rings should not be overlooked during routine maintenance or engine rebuilding.
Genuine Mercury Racing / Quicksilver OEM Part Number 816885
Over time, repeated heat cycles, vibration, fuel vapors, and normal service work can wear the adapter or harden the sealing O-rings. During air temperature sensor replacement, intake service, or powerhead rebuilding, inspection of the adapter and seals is recommended.
In the Mercury Racing parts illustration, the adapter is identified as Item #32, corresponding to OEM part number 816885. The sealing O-rings are identified as Item #31 and correspond to Mercury OEM part numbers 25-45711 and 45711.
Replacing the O-rings whenever the adapter is removed is inexpensive preventative maintenance that helps ensure proper sealing and long-term reliability.
Correct Mercury Racing Fitment
This genuine Mercury Racing / Quicksilver adapter fits Mercury Racing two-stroke crankcase-injected outboard engines with horns or slides.
These engines have powered some of the most successful Formula 1 tunnel boats, F1H20 race boats, Mod-U boats, offshore race boats, and outboard drag racing programs in Mercury Racing history.
Although small and often overlooked, the Mercury Racing OEM 816885 Air Temperature Sensor Adapter plays an important role in the EFI system found on Mercury Racing's legendary 2.5-liter two-stroke engines.
By providing a secure mounting point and proper seal for the air temperature sensor, the adapter helps ensure the ECU receives accurate intake air temperature information needed for consistent fuel delivery and engine performance.
Whenever the adapter is removed for sensor replacement, powerhead service, or EFI maintenance, inspecting or replacing the associated 25-45711 O-rings is good preventative maintenance. Fresh seals help maintain proper sensor retention and prevent potential air leaks around the adapter assembly.
Used on the Mercury Racing 260 EFI, 280 ROS, 300 Drag, and S3000, this genuine Mercury Racing / Quicksilver OEM component remains an important part of keeping these iconic 2.0 Liter Formula 1, offshore, and drag-racing two-stroke engines operating as Mercury Racing intended.
At Buckshot Racing #77, we continue supporting these legendary EFI platforms with genuine OEM parts, technical knowledge, and race-proven service components.
Includes One (1) x Mercury Racing / Quicksilver OEM ADAPTOR Part Number 816885 and two (2) x OEM O-RINGS Part Number 45711