1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 126Get this manual
Oil Injection System Troubleshooting Chart (Models with Warning Module) Troubleshooting the Oil Injection System
If problem occurs with the oil injection system and the warning horn sounds in pulsating manner, stop engine and check if problem is caused by (1) low oil level quart remaining, (2) the oil injection pump, or (3) faulty warning module1Open the engine cowling and check oil level in engine reservoirIf oil level is approximately one quart or less, the problem is low oil levelAdd oil to reservoir
NOTE: There is safety reserve of oil left in the reservoir after the low oil warning is soundedThere is enough oil for approximately 50 minutes of full throttle operation on four cylinder engines and approximately hour of full throttle operation on three cylinder engines2If there is more than quart of oil in the reservoir, then the problem may be in the oil injection pumpDO NOT run engine on straight gas when problem may be in the oil injection pumpEngine can be run by connecting remote fuel tank of 50:1 gas and oil mixture to engine