"Richard Malcolm" wrote in message I
have a Garmin GPS/Sounder and a small round in-dash depth finder.


The built in round one hardly works and the Garmen works poorly at mid
to high speeds.

First off, I would check the built in one carefully. Many of these in dash
units have a sensitivity adjustment, which is often a small screw type knob
in the back. It may just be that yours needs a little tweak. If you tell
us the make and model we might be able to help you out.

If you can get to the back of the dash, look at the depth sounder and see if
there is a small screw driver slot, possibly marked "sensitivity". Note
where it is adjusted now, in case you want to put it back.

If the sensitivity is too low it will have trouble getting any reading at
all in deeper water. If the sensitivity is too high, it will get false
readings, especially in shallow water. Be careful that the unit is not
indicating twice or three times the actual depth. when you are in very
shallow water.

As for operating poorly at speed, this is usually either due to
sound/vibration from the engine interferring with the sounder or water
turbulence creating air bubbles under the transducer. The transducer should
be mounted off to one side of the keel and NOT behind any thru hull
fittings.


My mechanic says that they all do that, but he suggest
replacing the in-dash one with a new one and new transducer, perhaps a
hummingbird. "Total cost for parts and labor around $400."

What do you poeple think?

I think that your could do this yourself and save $250.

Why do you need two depth sounders anyway?


Rod