1998+ Mercury Mariner 25HP Bigfoot Service Manual, Page 85Get this manual
IGNITION
Recommended Test (continued)
(1) (2) (3) (4) PROBLEMCONDITION Timing Will Not Advance Probable Cause Low Oil PressureEngine Over Heating:timing retards and fluctuates, rpm will remain below 2000 rpm (ECM) Low Oil PressureEngine Over Heating:timing retards and fluctuates, rpm will remain below 2000 rpm Ignition CoilHigh Tension Lead(s) Spark Plug Cap(s) 5k Resistor Spark Plug(s) (ECM) Unit Ground Connection:(ECM)ignition coilstator Engine Hard To Start Cold Debris In Carburetor Enrichener Circuit Weak Spark Condition Throttle Plate in Open Position Weak Spark Condition Vapor Lock Low Oil PressureEngine Over Heating:timing retards and fluctuates, rpm will remain below 2000 rpm Stator Ignition CoilHigh Tension Lead(s) (ECM) Spark Plug(s) Charge Coil Ignition CoilHigh Tension Lead(s) Spark Plug Cap(s) 5k Resistor Spark Plug(s) Ground Connection at:ignition coil(ECM)stator High Resistance To Ground at:stoplanyard switch (watercorrosion) (ECM) Boat Under Propped Propeller Hub Spun Perform Test No4 3