Just a quickie.... do you think it pays to send in a unit to have it repaired, (@ a 8 year old Lowrance X 85) or would it be wiser to replace it with something new?

Depends on what Lowrance wants to repair it, that's still a nice unit.  If it's not much more than $100 I would have it repaired if mine.  I have three X-75's and they are still my favorite units, even though I've bought several newer (supposedly better and higher pixel) units to upgrade them,  I keep going back to the X-75's