Vibration poses a significant issue for compasses in marine environments. The reason is that compass cards have a tendency to spin under the horizontal vibration frequencies generated by power boats. Unfortunately, the spinning card makes it difficult to get a proper reading from the compass. (Note that although there are some compasses that promise no-spin design, these units apparently have self-balancing issues.) In addition, even in cases where the vibration is insufficient to cause the card to spin, it can lead to excessive wear of the pivot.

What you need to do is to select the spot where you want to mount your compass and affix it with temporary measures while you test for vibration. Check out a range of engine RPMs and boat speeds because vibration is not uniform across the speed spectrum. Some speeds may, in fact, yield virtually no vibration, others a tremendous amount.

Try to mount your compass on the most solid surface available, a beam or deck, for instance, vice a panel, which is more susceptible to vibration. Even then, you may need to insert some foam rubber between the compass and the boat itself. This step should, at the very least, reduce the vibration, if not eliminate it altogether. Vibration-dampened binnacles are also on the market, and you may need to consider them in certain instances, such as if you have a slow-turning diesel engine.

- Linda Hoff