My boat is a fiberglass boat, and I believe (not 100% sure) that the
bottom of the boat near the transom is made from solid fiberglass.
Unfortunately, I don't see the "round black spot" that indicates the
best spot for gluing down the transducer that other people mentioned.
Well... I guess I will find out...

I understand that the possibility of losing some signal strength if I
use "shoot through hull" transducer. But this is acceptable. I am
planning to add a second transducer to the with the trolling motor at
the bow (for a second fishfinder) anyway. Therefore, I don't need to
get perfect signal strength from the "shoot through hull" transducer;
something acceptable is good enough.

Seem like everyone says that I should not glue the shooot-through-hull
transducer right at the center line. OK, I will have to move it off
from the center line and need to experiment in different spots in the
bilge area to find the best spot. Thanks for the warning.

Jay Chan


NOYB wrote:
wrote in message
ups.com...
I would like to get some info about fishfinder:

1. Is this OK to mount a "shoot through hull" transducer right at the
center line of the boat hull? The center line of the bottom of the hull
is smooth; therefore, I am not expecting any turbulent at the center
line. The reason why I ask is that we are not supposed to mount a
transom-mount transducer at the center line where the outboard motor is
to avoid the turbulent from the propeller. I am hoping that this
restriction only applies to transom-mount transducer, and doesn't apply
to "shoot through hull" transducer.

2. Is "shoot through hull" transducer good enough for scanning the sea
bottom for fishes? In other words, I would like to know if I can use
the fishfinder as a fish-finder instead of using it as a depth-sounder
if I use a "shoot through hull" transducer. I only intend to use the
fishfinder in shallow water, like 10-ft to 150-ft; hopefully, losing
some range will not be a problem.


"Shoot-thru-hull transducers are epoxied directly to the inside of
fiberglass boat hulls. The sound is transmitted and received through the
hull of the boat - but at the cost of some loss of sonar performance. (You
won't be able to "see" as deep with a shoot-thru-hull transducer as one
that's mounted on the transom.) The hull has to be made of solid fiberglass.
Don't attempt to shoot through aluminum, wood, or steel hulls. Sound can't
pass through air, so if there's any wood, metal, or foam reinforcement, it
must be removed from the inside of the hull before installing the
transducer. Another disadvantage of the shoot-thru-hull transducer is it
can't be adjusted for the best fish arches. Although there are disadvantages
to a shoot-thru-hull transducer, the advantages are considerable. One, it
can't be knocked off by a stump or rock since it's protected inside the
hull. Two, since there is nothing protruding into the water flow, it
generally works quite well at high speed if it is mounted where a clean
laminar flow of water passes over the hull. Three, it can't be fouled by
marine growth. "

IMO, the center line of the boat hull (aka--the keel) is probably not the
best spot for the shoot-through transducer because this is usually the
thickest portion of the hull.