Need Info on FishFinder
 

Shortwave Sportfishing wrote:
On 11 Jan 2006 11:02:48 -0800, "
wrote:

Seem like you have experience in both a transom-mounted transducer and
a shoot-through-hull transducer. I would like to ask you these
questions:

o Does the use of a shoot-through-hull transducer cut down the depth
of water that the transducer can scan but still maintain clear signal
to spot fishes that are within range? If this is the case, it will be
acceptable for me because I will only operate the boat in relatively
shallow water.

not per se, but it will degrade the performance.

o Does the use of a shoot-through-hull transducer not only cut down
the depth of water that the transducer can scan but also mess up the
signal to the point that I cannot use it to spot fishes even the fishes
are within range? If this is the case, I think I will only use the
signal from the shoot-through-hull transducer for a depth gauge, and
not for a fishfinder. And then I will need to add a second transducer
to the bow-mounted trolling motor for a fishfinder.

no, but again. the degradation of signal just means that it will not
be as sensitive to return signals as it ordinarily would be if it were
in the clear water. sonar transducers are designed and tuned in clear
water and not in a shoot thru configuration.

having said that,, sometimes the higher frequency transducers will see
epoxy and fiberglass as relatively transparent, but it has to be a
solid part of the hull - and i do mean solid.

as to mounting it center line, if you have a modified or deep vee,
it's not a good idea. they make pucks so that you can mount a
transducer on the inside of the hull angled so that it will shoot
straight down. I'm not a fan of centerline mounting as there can be
issues with uneven thickness of resin and glass.

the general rules about transom mounting are this - mount it such that
it will hang below the edge of the transom in clear water at least 18
inches away from the motor. most transoms are at a three degree angle
and the mounting bracket will allow you to adjust for that to keep the
transducer horizontal. if you have to mount it at the edge of the
transom, that's fine too, just make sure it's in clear water.

either way, it will work for you, it's just that transom mounting or a
true thru hull works much better than shooting through the hull.

thats a lot of typing for usign two fingers.

I appreciate the info that you have shared with me. Seem like I will
have to try installing a "shoot through hull" transducer to see if it
will work OK or not. And I will keep in mind of the suggestion of
using a high frequency transducer to overcome the resistance of the
hull.

Jay Chan