Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 100Get this manual
CHARG tNGSTARTING SYSTEM
No voltage reading; proceed to TE ST 3aDisconnect BLACK ground wire(s) from Test Point 2bConnect vollmeter between common engine ground and Test Point 2cTum ignition key toStart" position
Battery Voltage
aReconnect BLACK ground wire(s)bConnect voltmeter between common engine ground and Test Point 3cTurn ignition key to Start" position
12 Volt Reading
Check BLACK ground wire for poor connection or open circuilReconnect ground wire to start er solenoid; proceed to TEST 7
No voltage reading; proceed to TEST 4
12 Volt Reading
Defective starter solenoid
Electric Start Tiller Handle Model
Neutral start switch is open or BLACK leads are disconnected or damaged
No vollage reading; proceed to TEST 5aConnect voltmeter between common engine ground and Test Point bTurn ignition key toStart" position
12 Volt Reading
Neutral start switch is open, or YELlOWf RED or BLACK wi re is open between Test Points and 3
No voltage reading; proceed to TEST 6Connect voltmeter between common engine ground and Test Point 5