I have not had great luck with my Garmin in my R25sc however, many of the professional fishing guides that fish off of the coast think it is the best one- some of these guys put 1000's of hours on their boats each season. So there is a diversity of opinion on this topic. Mine has never truly been tweaked but I am going to have a Garmin tech do it this month while on the water since I purchased a new nav unit. After a failed pump last year I found out that you need to operate the pump on a regular basis, otherwise it could freeze up (or so I was told). You do this by turning the ignition to the on position, turning on the chart plotter and autopilot, engaging the autopilot, then alternately pressing the arrow keys that would normally correct the course port and starboard. This will move the rudder while you are not in the water.
Good luck
As a post script- after watching Ranger's guys replace the pump unit last year I would not dream of doing this myself. It would be total self abuse.