I have a Lowrance LMS-337C DF combination gps/charplotter/sonar unit.
Just recently bought it and haven't installed it yet. It came with a
transom mount transducer. Do I need to buy a thru-hull transducer (for an
additional $300) for this unit. Of note, I think, is the fact that my boat
is an inboard engine. I'm running a 26 ft. LOA, 10.5 ft beam, single screw
inboard in salt water with depths in my area usually from 30 to 150 ft. The
Lowrance thru-hull accessory for this is part 106-79 which is a 50/200 kHz
transducer and best price for this is around $279 before shipping and taxes.

I've gotten mixed advice on this. Most people tell me the transom mount is
fine but when talking to tech support at Lowrance they answer in a manner
that suggests they don't know for sure and when I point out it's an inboard
engine, they end up saying "It might be a good idea if you go with the
thru-hull." Well, for $300 additonal, plus mounting costs I'd like to be
absolutely CERTAIN it's a good idea!!

Any help would be appreciated. Thanks in advance.

Chet

What type hull? Fiberglass hulls pass signals well and you can glass
the head to the hull directly, or epoxy a pipe mount to submerge the
sounder in oil. You can try the transducer location in a baggie of
water held against the hull on the inside.

Wood hulls need a window made of material that will pass the ping, or
an external mounting.

The location must avoid air bubbles at speed and at rest.

Terry K

CGB wrote:
I have a Lowrance LMS-337C DF combination gps/charplotter/sonar unit.
Just recently bought it and haven't installed it yet. It came with a
transom mount transducer. Do I need to buy a thru-hull transducer (for an
additional $300) for this unit. Of note, I think, is the fact that my boat
is an inboard engine. I'm running a 26 ft. LOA, 10.5 ft beam, single screw
inboard in salt water with depths in my area usually from 30 to 150 ft. The
Lowrance thru-hull accessory for this is part 106-79 which is a 50/200 kHz
transducer and best price for this is around $279 before shipping and taxes.

I've gotten mixed advice on this. Most people tell me the transom mount is
fine but when talking to tech support at Lowrance they answer in a manner
that suggests they don't know for sure and when I point out it's an inboard
engine, they end up saying "It might be a good idea if you go with the
thru-hull." Well, for $300 additonal, plus mounting costs I'd like to be
absolutely CERTAIN it's a good idea!!

Any help would be appreciated. Thanks in advance.

Is that a planing hull or more of a deep V? If you have a swim platform
or anything like that on the back, you might try the included in the
price transducer and see how well it works. Make a temporary mount and
give it a test drive.

Speed does not bother a transducer as much as it being in highly
turbulent/air bubble laden water. If you're moving at reasonable speeds
and can keep the transducer off to one side and well wetted in fairly
clean water it might work fine.

I've always liked the concept of an externally mounted and easily
removable transducer.

Jack

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

In answer to the questions from Terry and Jack, it is a fiberglass hull and
it is a modified V which is a planing hull. The boat is heavy, and does get
up on plane with the help of trim tabs. I could try it on the transom (no
swim platform) or with a water filled baggy in the bilge, but once it's in
the water, it stays until it's pulled for storage in the fall. If I put it
on the transom and it doesn't work, then it will have to stay there and be
re-done next year. I don't want the cost of pulling the boat and having a
thru-hull installed and then relaunched. It would cost me over $100 just to
have the boat hauled by a marina. This is not a trailerable boat. It has
an 11' beam and a flybridge and single inboard engine.

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

Chet

In article , Jack Erbes wrote:
CGB wrote:
I have a Lowrance LMS-337C DF combination gps/charplotter/sonar unit.
Just recently bought it and haven't installed it yet. It came with a
transom mount transducer. Do I need to buy a thru-hull transducer (for an
additional $300) for this unit. Of note, I think, is the fact that my boat
is an inboard engine. I'm running a 26 ft. LOA, 10.5 ft beam, single screw
inboard in salt water with depths in my area usually from 30 to 150 ft. The
Lowrance thru-hull accessory for this is part 106-79 which is a 50/200 kHz
transducer and best price for this is around $279 before shipping and taxes.

I've gotten mixed advice on this. Most people tell me the transom mount is
fine but when talking to tech support at Lowrance they answer in a manner
that suggests they don't know for sure and when I point out it's an inboard
engine, they end up saying "It might be a good idea if you go with the
thru-hull." Well, for $300 additonal, plus mounting costs I'd like to be
absolutely CERTAIN it's a good idea!!

Any help would be appreciated. Thanks in advance.

Is that a planing hull or more of a deep V? If you have a swim platform
or anything like that on the back, you might try the included in the
price transducer and see how well it works. Make a temporary mount and
give it a test drive.

Speed does not bother a transducer as much as it being in highly
turbulent/air bubble laden water. If you're moving at reasonable speeds
and can keep the transducer off to one side and well wetted in fairly
clean water it might work fine.

I've always liked the concept of an externally mounted and easily
removable transducer.

I like inboard transducers, but I have had problems. I have a transom mounting
plate that is used to mount anything on the transom. You can unmount devices
and the plate is permanant.

greg

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)