I have Standard Horizon depth, wind and knot/log on my 1991 Hunter 30T. Up until fairly recently they have been great, reliable instruments. I do most of my sailing in fresh water but take a two to three week cruise in salt water every summer. Three summers ago, not long after I sailed into salt water, my knot/log just stopped functioning. Of course I checked the obvious; jammed impeller, broken wire, etc. After I came back to fresh water, it eventually started again. Same story last year and again this. The only thing I can think of is the higher density of the salt water is exacerbating some sort of ground short. But where? Any thoughts? Mike McKendy Sea Sharp