Tom my 76c for the most part allows me to do what your talking about. I can go by a tree sticking out of the water. And it always shows the same on it. but today when going 5 MPH. It was not showing the same Lad and Lan? Would not have thought that speed would be a factor?
And wonder if the unit was just not getting the signal it does most days?

Now my 987c-SI GPS does show the same bouey in the same place all the time. and its close enough to run by at night. But I always wonder if it may be off enough to cause me to run over a marker? So I for one do not put full faith in it yet.
Will check this again next day I am out on the water. and give you the findings of the Garmin 76C
Shoot Come to think of It I can also do it in the yard on the 4 wheeler also.

How is our buddy Todd doing? If my stress test goes well Friday. I need to get with him and go Striper fishing next week. He likes the pole dancers while striper fishing LOL
Pete