CGB wrote:
snip
No one (except some reading I've done from transducer sellers, and that's
the hitch) seems to be saying that transom mount is out of the question.
Several marinas have told me it's OK but when I show them the literature
that comes with the products they sell they then back off and said it
"should" work but if I have them do it ($$) they know how and would "prep"
the boat before putting a transom mount on. I.e. not much confidence is
being inspired

I understand lack of confidence thing. They're going to get paid and
the work can get a little open ended on costs as they proceed. I'm
"thrifty" (maybe even cheap :)).

Is the boat in the water? I'd test the transom mount pier side fastened
to a broom handle and I'd also probably test it in a baggy and/or
submerged in the bilges.

You need to find a spot in the bilges with puts the transducer shooting
through pretty much nothing but fibreglas saturated cloth or wood (no
layers of foam, balsa, etc.).

Once you get a feel for where it will work you can move on to some
underway testing for the effects of speed and turbulence. I have a 14'
Scott flat bottomed canoe that I love to fish Maine lakes from. It will
do about 25 knots and the transom mount readings start to go to hell at
15 knots or so and up. But at normal potting around speeds it performs
faultlessly.

I have mixed feelings about the purpose and usefulness of transducers.
I'm not a person that thinks they will keep me from running around. I
think of them as something that will show me bottom details and fish and
I don't expect to do that at high speeds.

And it is incidental that, if I'm underway and moving, they are also a
thing that might show me a trend that tells me that I am likely to run
aground if I don't do something. I can tell you from experience that
you can run aground with the end that does not have the transducer on it
while showing plenty of water on the end that has a transducer.

But it I could find a shoot through the hull location where the transom
mount transducer worked to the purposes you most want, I'd put the
transom mount there and leave it. I love the concept of no holes and
nothing hanging off.

I'd swap the baggy for something more permanent like a tubular fibreglas
well trimmed for a vertical mount, glassed in place, and filled with
mineral oil.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)