From time to time even the most reliable compass may need repair. Sometimes the seals will go bad or the dome will crack or break, causing the compass to lose fluid. These are both situations that require compass repair by a professional. There are other times when small variations in temperature will cause bubbles to form in the compass. Although these are not harmful or an indication of other problems with the compass, some boat owners insist on removing these bubbles. Refilling a compass with fluid is a relatively simple process, easily accomplished by most boat owners.
Remove the compass from the compass mount on the vessel. Boat builders have their own individual methods for mounting a compass. Consult the owner's manual of the specific vessel for instructions on removing the compass.
Open a container of compass oil. Fill a manual industrial syringe with compass oil by inserting the tip of the syringe into the compass oil and drawing the plunger of the syringe back. Set the syringe aside, ensuring that the syringe is easily accessible.
Locate the filling screw on the side of the compass. Position the compass so that the filling screw is facing upward. Remove the filling screw by turning it counterclockwise with a screwdriver. Jostle the compass gently to bring any trapped air bubbles to the fill hole.
Hold the compass in one hand and pick up the syringe with the other hand. Insert the tip of the syringe into the fill hole of the compass and inject enough compass oil into the compass to fill it. Gently jostle the compass as before to ensure that there are no other trapped air bubbles in the compass.
Thread the filling screw clockwise into the compass fill hole and tighten it with the screwdriver.
Shake the compass vigorously to release any air that may still be trapped in the compass. Top off the compass oil as needed. Reinstall the compass in the boat.
Do not move the compass once the filling screw has been removed except to gently jostle the compass to release any trapped air.