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Shoot-thru-hull vs. Transom Mounting
In a shoot-thru-hull installation, the transducer is bonded to the inside
of the hull with epoxy. The sonar "ping" signal actually passes through
the hull and into the water. This differs from a bolt-thru-hull
installation (often called simply "thru-hull"). In that case, a hole is cut in
the hull and a specially designed transducer is mounted through the
hull with a threaded shaft and nut. This puts the transducer in direct
contact with the water.
Typically, shoot-thru-hull installations give excellent high-speed
operation and good to excellent depth capability. There is no possibility
of transducer damage from floating objects, as there is with a transom-
mounted transducer. A transducer mounted inside the hull can't be
knocked off when docking or loading on a trailer.
However, the shoot-thru-hull installation does have its drawbacks.
First, some loss of sensitivity does occur, even on the best hulls. This
varies from hull to hull, even from different installations on the same
hull. This is caused by differences in hull lay-up and construction.
Second, the transducer angle cannot be adjusted for the best fish arches
on your sonar display. (This is not an issue for flasher-style sonars.)
Lack of angle adjustment can be particularly troublesome on hulls that
sit with the bow high when at rest or at slow trolling speeds.
Third, a transducer CAN NOT shoot through wood and metal hulls.
Those hulls require either a transom mount or a thru-hull installation.
Fourth, if your Skimmer transducer has a built in temp sensor, it will
only show the temperature of the bilge, not the water surface temp.
Follow the testing procedures listed in the shoot-thru-hull installation
section at the end of this lesson to determine if you can satisfactorily
shoot through the hull.
Transom Transducer Assembly And Mounting
The best way to install these transducers is to loosely assemble all of the
parts first, place the transducer's bracket against the transom and see if
you can move the transducer so that it's parallel with the ground.
The following instructions sometimes vary depending on the mounting
bracket that came with your transducer. Single-frequency Skimmers
come with a one-piece stainless steel bracket, while dual-frequency
Skimmers come with a two-piece plastic mounting bracket. Use the set of
instructions that fits your model.
1. Assembling the bracket.
A. One-piece bracket: Press the two small plastic ratchets into the
sides of the metal bracket as shown in the following illustration. Notice