1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 51Get this manual
No voltage reading; proceed to TEST 3 TESTDisconnect BLACK ground wire(s) from Test Point 2bConnect voltmeter between common engine ground and Test Point 2cTurn ignition key to "Start" position12 Volt Reading Check BLACK ground wire for poor connection or open circuitReconnect ground wire to starter solenoid; proceed to TEST 7
TESTReconnect BLACK ground wire(s)bConnect voltmeter between common engine ground and Test Point 3cTurn ignition key to "Start" positionNo voltage reading; proceed to TEST 412 Volt Reading Defective starter solenoidTESTConnect voltmeter between common engine ground and Test Point 4bTurn ignition key to "Start" position
No voltage reading; proceed to TEST 5
12 Volt Reading Neutral start switch is open, or YELLOWRED wire is open between Test Points and 312 Volt Reading Defective ignition switch
No voltage reading; proceed to TEST 6
TEST Connect voltmeter between common engine ground and Test Point 5