We had the auto pilot on for 3 days and nights on a passage. We were on a downwind passage in 6 foot seas . The motor worked so hard the solder melted, the brushes fell off and the motor failed. It took me hours repairing it on the salon floor while on the passage.
The problem was that Raymarine put the motor in a metal cover to make it look good so it heated up. They probably didn't think anyone would use the auto pilot for more than a few hours at a time. They've since corrected the problem taking the shell off and adding aluminum cooling fins.