Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 75Get this manual
Wiring Connections Speedometer
Tachometer
Figure Without Light Switch
NOTE: ANY IN STRUMENT WIRING HARN ESS LEADS NOT USED MUST BE TAPED BACK TO THE HARNESS Speedometer
Tachometer
Figure With Light Switch
a Tachometer ReceptacleFrom Control Box or IgnitionChoke SwitchTachometer Wiring Harness
cLead to Optional Visual Warning Kit (Taped Back to Harness)