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Writer's pictureMike Hill

Mercury 2.5 Liter 2-Stroke Factory Timing Specs

The timing specifications for a 1991–1999 Mercury 2.5 Liter 2-Stroke V6 outboard typically vary depending on the specific model (150, 175, 200, 225, XR6, carbureted, EFI, or high-performance versions such as the SST-120, 245 HP, 260 ROS, 280 Race/Consumer, 300 Drag, S3000).


Here are the general timing specs for this range:


  1. Base Timing (Idle Timing)

    • Carbureted Models: 0-8 degrees BTDC (Before Top Dead Center) at idle.

    • EFI Models: 0-10 degrees BTDC at idle.

    • Best to set this while idling and to the desired idle RPMs, base timing is the correct way to set idle on these motors.


  2. Maximum Advance Timing (WOT Timing)

    • Standard/Carbureted Models: 21-25 degrees BTDC at wide open throttle (WOT).

    • High-Performance Models: Up to 25 degrees BTDC at WOT, depending on the specific model.


  3. Idle Speed:

    • 600-700 RPM in gear.


Additionally, always verify timing with a timing light while following the manufacturer’s recommended procedure for your specific engine.






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