1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 235Get this manual
Electrical System Troubleshooting General Checks
Before troubleshooting the Power Trim electrical system, check the following: 1Check for disconnected wires
2Make certain all connections are tight and corrosion free3Check that plug-in connectors are fully engaged4Make certain battery is fully chargedRefer to the preceding wiring diagrams for connection points when troubleshooting the electrical system(Connection points are specified by number
Troubleshooting the "Trailer" Circuit (When "Up" Circuit Is OK)
Remote Control Equipped with Trailer Button Use an Ohmmeter (R scale) and check continuity of wire between Point 10 on "Up" solenoid and Point 13 on trailer buttonIf no continuity, wire is open
If wire is OK, disconnect all battery leads from battery and check continuity across trailer button terminals with trailer button depressedIf no continuity is indicated, trailer button is faulty
Troubleshooting the "Up" and "Trailer" Circuits (Both Circuits Inoperative: "Down" Circuit Is OK)