My first reaction is the wiring or the mounting; they don't all do that.
A poor electrical ground connection can cause anything to not work or be
erratic.
Transducers must be correctly mounted so that they are in clear, non
turbulent water.
$400 for parts and labor is not unreasonable, but I wouldn't pay your
mechanic to do a job that he doesn't think you should expect to work
reliably.

"Richard Malcolm" wrote in message
om...
it is that time of year again. I have a 25' four winns that I keep in
the water for 8 months or so. When it is not in the water it is at
some marine storage area. Since I don't own a trailor, I have my local
four winns people winterize it. Since I don't have a trailer, I must
get everything that needs to be done to it when it is out of the
water, done now.
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. 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?