In article ,
"Lynn Coffelt" wrote:

wrote in message
ups.com...
I have purchased a garmin depth finder,gps unit. It seems to lose
bottom above 9 knots in salt water. This is installed on a 16'
carolina skiff. Before this unit i had an eagle depth finder and it
did the same way. I though maybe it was a bad unit so i bought this new
and undated unit and it seems to do the same way. I have been told it
is because it is on a flat bottom boat but i have to belive there is a
way to mount it so this does not happen. Maybe i need to adjust the
height but it is installed as per the mfg. instructions. It is a
transom mount. Any advise would be very helpful.

Thanks,
Sidney

I'm not familiar with the Carolina Skiff hull, but there is a fairly
easy way to find a good location and angle for a transom mount transducer.
Assuming that you are able to lean a bit over the transom while underway,
just fasten the transducer on a piece of flat board that you can manually
raise, lower, shift side to side and change the face angle while running.
either just hold the board by hand or temporarily clamp the board in various
test positions.
YMMV, but hey, it often makes quick work of a vexing situation!
Old Chief Lynn



Another very common cause of this problem is "Air Bubble Effect" of
turbulance across the transducer face. The faster the skiff goes
the more air gets pushed down along the hull bottom and as those
"Air Bubbles" cross the transducer face, they change the density
of the liquid that the transducer couples it's UltraSonic pulse
into and reduces the effective coupling into the water. Bubble
Deflectors are used on non-Planing hulls to fix this eventuality,
but on planing hulls it is problematic at best to get soundings at
high speed.

Bruce in alaska
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