2001 Mercury Mariner 50-60HP Factory Service Manual, Page 134Get this manual
TIMING, SYNCHRONIZING,ADJUSTING
CAUTION
When using the old style mercury filled carbtuner (91-809641) install filters (4) in each lineThis will prevent mercury from being drawn into carburetors during an abrupt throttle change
WARNING
When revving the engine move the throttle cam to increase RPMDo not use remote control or tiller handle twist throttle to increase RPMIf you do, the throttle linkage will contact the bottom intake manifold hose adaptor and damage the fitting6Rev engine few times and let engine idle for 15 secondsCheck that the vacuum values remain the same between cylindersRe-adjust if necessary7Stop engine, remove adaptors and reinstall plugsRefer to Idle Speed Adjustment and adjust the idle RPM back to specification