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