Maintaining your Mercury outboard's hydraulic tilt system will ensure that your system works as well and as long as your engine, and perhaps longer. One major factor in the wear of hydraulic systems, like your tilt system, is operating without the correct amount of oil, or the wrong kind of oil. Be sure to follow the recommendations in your tilt system's operating manual for recommendations on the type and weight of oil to be used and check the level regularly as part of your regular maintenance schedule.
Items you will need
Recommended oil
Oil can with a flexible spout
Raise your motor using your tilt control.
Find your trim pump. The easiest way to do this is by following the oil line from the tilt system, back toward your tilt control, or from your tilt control. While the pump is located in different places on different boats, with a Mercury outboard, it's usually tucked under some deck access plat in the rear of the boat.
Unscrew the recessed screw cap, usually on the front right corner of the pump. This is the oil filler cap. Remove the cap completely.
Check the oil level in the pump. The oil should come up to the second thread on the filler spout. Use your oil can with a flexible hose to fill the oil up to that level.
Raise and lower the motor about six times to bleed air out of the system. Screw the oil pump filler cap back on.