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

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
--
add a 2 before @

It's aeration in the flow of water over the transducer, the only
solution is to get the transducer into clear water. Get your boat up to
speed and look over the back of the baot where the transducer is, if it
is all chrrned up then that is your problem. Lok across the transon
and see if there is an area where the water is clean(ish), this is
where the transducer is most likely to work. If there are no clean
sections, then you can try going lower into the water with the
transducer, but then you run the risk of knocking it off! .

Geoff's got it dead on. If you really want to get a reading at speed
you usually have to put the tranducer deeper. This most likely will
creat rooster tails and added resistence to your planing hull. It will
also pick up more seaweed and crap.

You might be able to avoid some of this by mounting it way forward on
the hull, but of course this raises the issue of, how to clean it when
you are out on the water without having to jump in under the boat.
This still has problems, though, because in a light chop the hull
probably won't have a clean spot and you will constantly be getting
air bubbles flowing over the transducer as you bounce causing it to
loss the bottom.

So that gets back to the mount it on a stick and move it up and down
on the hull idea. It would be a great idea because you could make the
stick removeable and then you could scan side to side or point it back
at your fishing line and see how deep you are trolling.


On 14 May 2006 17:05:40 -0700, "
wrote:

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