A boat compass is one of the most important instruments on the boat. Magnetic compasses are reliable and last a long time. After a few years and long exposure to salt water and the sun, a compass may require repair work. Cold climates can also damage a boat compass. Repairing a compass will save you hundreds of dollars. The most common problems with a boat compass are air bubbles in the fluid and a sticky dial. Bubbles are often caused by leaks, which you can repair by replacing gaskets or tightening screws. A sticky dial may require replacement parts.
Test the compass to make sure that the dial is stuck. Write down the reading on the compass. Use a magnetic screwdriver, or small magnet, to deflect the dial five degrees to port by moving the screwdriver close to the compass on the port side (the left side of the boat when facing toward the front or the bow).
Move the screwdriver away from the compass and observe whether the compass returns to the original reading. Cause the needle of the compass to deflect to starboard by moving the screwdriver close to the compass on the right side. Remove the screwdriver and observe whether the compass returns to the original heading.
Replace the pivot and jewel in the compass if the needle does not return to the original heading following the magnet test. Purchase a replacement pivot and jewel. Purchase replacement fluid and replacement gaskets for your brand of compass.
Remove the compass from the housing base and disassemble the compass by removing the screws that hold the dome in place. Drain the fluid and remove the old gaskets. Lift the old pivot and jewel out of the compass and replace it.
Replace the gasket with a new one. Replace the dome and tighten the screws securely, but be careful not to crack the dome. Invert the compass and refill it with a manufacturer's recommended compass oil.
Bubble in Oil
Remove bubbles from the compass fluid by inverting the compass. Remove the install/fill plug on the bottom of the compass. Replace lost fluid by refilling the compass with compass oil.
Check the diaphragm for leaks by pressing on it. Replace the diaphragm and the gasket if oil leaks out. Disassemble the compass by removing the screws with a small screwdriver. Drain the fluid and then replace the gasket and the diaphragm.
Replace the oil and install the fill plug tightly. Gently press on the diaphragm while filling the dome with compass oil to prevent air from leaking back into the dome. Verify that each screw is tightened securely to prevent oil leaks, which will cause new bubbles to form.
Items you will need
Remove the compass and store it in a warm place during cold weather and when not in use to avoid damage from the sun and from freezing temperatures.
Do not attempt repairs on a boat compass unless you are confident of your skill. The compass is critical to navigation and must be accurate.
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