I have an operational Datamarine Depth gauge on my C&C. However, after careful inspection, the back of the unit appears to be very corroded. I checked the Datamarine web site and the tech reps indicate that units can be sent back for repairs. Not quite sure what the service center will do with this unit - replace the back of the unit? Have anyone had any preventetive maintenance done with Datamarine? Is it worth it to fix up a 20 year unit or just buy a new one? Any recommendation on what a low cost new depth gauge should go for?Thanx for insights.