I would try and find out if there is something magnetic onboard that is causing your problems. Bring a handheld compass aboard and take readings in different locations (including near but not right next to the boat's compass and fluxgate sensor). You can use a the handheld compass to "hunt" for a source of magnetic interference. If the handheld readings are ok everywhere, then I would suggest that you troubleshoot the problems separately. You can "swing" the main compass yourself and at least get it to be somewhat accurate - Google can help you find specific instructions for your unit. The fluxgate should be tested as per http://www.raymarine.co.uk/knowledge....cfm?view=3798
to make sure it is working ok.