I installed a fancy auto-pilot, no, I should say, I 'assisted' an electronic genius install a hydrolic-electric auto-pilot last year. This was in a 50ft power-vessel. We found out, by several 'tests' that the location of the FLUXGATE was absolute. It would work fine on one course but take an immediate right turn on another. We talked to the dealers, experts, and electronic people world-wide. The consensus is, the fluxgate must be mounted as far, three ft minimum, from the engines as possible, in the centerline of ship if practicable, and low, but not submerged in the bilge. Use nylocks or at least a GOOD lok-tite for the mounting bolts on all brackets. I have had several of them loosen on different boats, and like a Limie bike, you'll be tightening forever.