2001 Mercury Mariner 50-60HP Factory Service Manual, Page 128Get this manual
TIMING, SYNCHRONIZING,ADJUSTING
WARNING
To prevent personal injury or possible death, from loss of balance or stability while servicing the motor, DO NOT attempt to check timing while boat is in motionFailure to follow one of the recommended servicing procedures may result in the person falling overboard or causing personal injury from fall in boat
WARNING
To prevent personal injury from spinning flywheel, Do Not attempt to remove flywheel cover or place hands on top of cover when checking ignition timingIgnition timing is not adjustableThe Electronic Control Module unit electronically controls the ignition timingWhen initially running the outboard, use timing light to verify that the ignition timing falls within the timing windows as described within the following testsIf the ignition timing does not stay within the timing windows, replace the ignition E.C.Munit and retest(Refer to the Ignition Diagnostic Procedures tests in Section 2A IMPORTANT: When checking the timing with the engine running, one of the following test procedures must be followedCheck maximum timing per specification while running the outboard: IN TEST TANK ON DYNAMOMETER ON BOAT SECURED ON TRAILER "Backed in Water" 1Attach timing light to #1 spark plug lead