1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 281Get this manual

Troubleshooting the "Up" Circuit (When "Down" Circuit is OK) Connect Voltmeter RED lead to Point 10 and BLACK lead to groundDepress the "Up" trim button
Battery Voltage Indicated: Connect Voltmeter RED lead to Point 3
No Voltage Indicated: There is an open circuit in wires (BLUEWHITE, PURPLE-WHITE, or PURPLE) between "Up" solenoid and trim switch
Battery Voltage Indicated: Connect Voltmeter RED lead to Point 6
No Voltage Indicated:

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives