Oil Pressure Prob - Thank You Speedwakers!!!

Marine wiring color codes:

Blk -Grounds-General
Blk/Brn -Pump Grounds
Blk/Red -Voltmeter Grounds
Blk/Org -Isolated Accessory Grounds
Blk/Yel -ignition stop
Blk/Grn -Water Level Sender Ground
Blk/Blu -Lighting Grounds
Blk/Gry -Nav Light Grounds
Blk/Wht -Battery Parallel Solenoid
Brown -Pumps-General, Bilge or Sump (Manually Switched)(Also alternator starter to Ign.)
Brn/Red -Pumps, Bilge or Sump
Brn/Org -Power feed to Auto Bilge Switches-Pumps, Fuel/Oil Tranfer or Priming
Brn/Yel -Baitwell or Aerator
Brn/Grn -Fresh Water Pump/Water Maker
Brn/Blu -Head Pump
Brn/Vio -Washdown Pump
Brn/Wht -trim pos sender
Red - Battery Feeds Unprotected
Red/Vio -Misc. Accy. Main Feed Protected (fused) from batt to trim panel.
Pink -Fuel Sender
Org/Blk -Audio System Feed
Org/Brn -Electric Head-Sanitation System
Org/Red -Wiper Port
Orange -Accessories common feed- Dist Panel to Acc switch-Anode Electrode-Mercathode
Org/Yel -Diesel Pre-heat
Org/Grn -Wiper Stbd
Org/Blu -Communications Equipment
Org/Vio -Navigation Equipment
Org/Wht -Wiper Center
Yel/Blk -Choke - Neutral saftey trans mounted
Yel/Red -Start Solenoid(starting circut), Neutral Safety
Yel/Org -Powered Ventilation, Fans
Yellow -Bilge Blowers -(also alternator DC output)
Yel/Wht -Rudder Angle Sender
Grn/Red -Stop Solenoid/Kill Switch
Grn/Yel -AC Grounding
Green -Bonding
Grn/Wht -Engine Trim in and or tilt down
Grn/Org -Engine Independent Trim down
Blu/Blk -Cabin Lights
Blu/Brn -Oil Temp Send
Blu/Red -Cabin or Cockpit Lights Port
Blu/Org -Engine Independent Tilt Up
Blu/Yel -Lighting Circuits to Remote Send
Blu/Grn -Cabin or Cockpit Lights Stbd
Blu -Instrument & General Lighting
Blu/Vio -Courtesy, Boarding Lighting
Blu/Wht -Engine Trim Outand/or Tilt Up
Light Blue -Oil Pressure
Vio/Red -Eng. or Generator B+ from Breaker
Vio/Yel -I/O Trim Up (ballast bypass)
Vio/Grn -I/O Trim Down
Vio -12v Ignition-Generator or Engine
Vio/Wht -Trim "Trailer" switch
Gry/Blk -Mast Light
Gry/Red -Spotlight Remote
Gry/Org -Docking Lights
Gry/Grn -Strobe or Beacon
Gry/Blu -Spreader/Flood Lights
Gry/Vio -Windlass/Winch
Gray -Navigation (running) Lights, Tach. Send
Gry/Wht -Anchor Light
Wht/Brn -Temp. Alarm or Indicator
Wht/Red -Fuel Alarm or Indicator -((Ignition module to Dist.)Mercury Thunderbolt Ignition)
Wht/Org -Fire Alarm or Indicator
Wht/Yel -Air Flow Alarm or Indicator
Wht/Grn -Water Press/Flow Alarm or Indicator - ((Ignition module to Dist.)Mercury Thunderbolt Ignition)
Wht/Blu -Oil Press Alarm or Indicator
Wht/Vio -Voltage Alarm or Indicator
White -General Alarm Usage, Yamaha Kill Switch
Tan - Water Temp sender
Tan/Blu -Warning system sense wire (Audio warning)
Pink -Fuel sender


The purple wire sounds to me like 12V +. Maybe it is the hot wire to the gauge? If you really had zero oil pressure, your alarm would be sounding. Likely a gauge issue.