1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 240Get this manual
Troubleshooting the "Down" and "Up" Circuits (All Circuits Inoperative) Remote Control NOT Equipped with Trailer Button Check two in-line fuses (under cowl) to see if fuses are blown
Blown Fuse: Correct problem that caused fuse to blowD Replace fuse
Fuses Not Blown: Connect Voltmeter red lead to Point 3, and black lead to groundBattery voltage should be indicated
No Voltage Indicated: Check battery leads and RED leads (between engine starter motor solenoid and Point 3) for poor connections or open circuitsD Check battery charge
Battery Voltage Indicated: Connect Voltmeter RED lead to Point 10 and black lead to groundD Depress "Up" trim button and check for battery voltage
Battery Voltage Indicated: Check BLACK ground wires at solenoids for poor connection or poor groundD Check BLACK motor lead for poor ground at Point 12If wire is grounded, the pump motor is faultyRefer to "Motor and Electrical TestsRepair," following
No Voltage Indicated: Connect RED Voltmeter lead to Point 5, and BLACK lead to ground