Make sure your MAX is calibrated every time you go sailing. Calibration can be done in two ways. You need to do it right before the moment you mount MAX to your boat.
1A. (BASIC) COMPASS CALIBRATION
Make an infinity sign twice with MAX in your hand (see picture below). This movement needs to be done in a smooth manner, in a width of 30 centimetres and as close as possible to the location where you want to mount MAX.
1B. (ADVANCED) COMPASS CALIBRATION
Your compass is calibrated! You can now mount MAX to your boat.