Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 46Get this manual
No voltage fead lng;
Disconnect black ground wirers) from Test Point 2(Figure 4) bConnect voltmeter between common engine ground and Test Point 2Turn ignition key 0 "Slarl" position
Balle,)' VoLtage
proceed 10 TEST 3
Reconnect black ground wire Connect voltmeter between common engine ground and Test Point 3b
12 Volt Reading"
Check black ground wire for poor connection or open circuitReconnect ground wire 10 starler solenoid; proceed to TeST 7
,Turn ignition key to "Start" posilion
No voltage reading;
proceed to TE ST 4
12 Volt Reading
Defective starter solenoid
No vollage roadlngproceed to TE ST 5