1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 65Get this manual
TimingSynchronizing Adjusting (4 Cylinder Models) Specifications
Models 100115 Full Throttle RPM Range Idle RPM (in "FORWARD" Gear) Maximum Timing 3000 RPMCranking Speed) Idle Timing Spark Plug 47505250 650700 23_ B.T.D.C(25_ B.T.D.C 2_4_ B.T.D.CNGK BP8H-N-10 [0.040 in(1.0mm) gap] NGK BPZ8H-N-10 [0.040 in(1.0mm) gap] NGK BUHW 1-3-2-4
Timing Pointer Alignment WARNING
Engine could start when turning flywheel to check timing pointer alignmentRemove all spark plugs from engine to prevent engine from starting1Remove aft cowl support bracket2Install Dial Indicator 91-58222A1 into no1 (top) cylinder3Turn flywheel in clockwise direction until no1 piston is TDC, then set Dial Indicator at "0" (zero)