ATAT Performance and Buckshot Racing #77 proudly introduce a precision-engineered Billet Big-2-Small Conversion Top Cap made from aerospace-grade 6061 CNC Billet Aluminum.
 
This billet top cap is specifically designed for Mercury Racing 2.5-liter EFI outboards, including the 280 ROS, 300 Drag, and S3000 blocks.
 
It serves a critical role in converting a 2.5 block intended to run a big bearing crank (OEM part #848330T4) to accept a small bearing crankshaft (OEM part #455-848330A1), giving performance builders and racers greater flexibility when building or modifying Mercury 2.5 engines.
 
This billet top cap replaces the OEM 849366T1 top cap found on big bearing motors and mimics the geometry and function of Mercury’s 848282A1 and 1159-848282A1 small bearing top caps.
 
However, it is manufactured to tighter tolerances and enhanced durability using high-quality billet aluminum.
 
Designed for drop-in installation, it allows you to run small bearing crankshafts in a big bearing block without any machining or modifications.
 
That makes it a perfect solution for racers wanting to reuse big bearing blocks with more readily available small bearing cranks.
 
The cap is precision CNC-machined to ensure perfect crank alignment and long-term reliability. It features a machined raw finish and is corrosion resistance with a professional-grade appearance.
 
Whether you're racing a 2.5 Drag, fine-tuning a 280 ROS, or rebuilding an S3000, this billet top cap offers the strength and precision your high-performance outboard demands.
 
This billet top cap is available now through ATAT Performance in Australia and Buckshot Racing #77 in the USA—two trusted names in Mercury 2.5 high-performance parts and racing innovation.
 
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.