Shoot-Thru-Hull vs. Transom Mounting

If you cruise or fish around lots of structure and cover, your transducer may be frequently kicking up from object strikes. If you wish, you may move the transducer a little higher for more protection.

There are two extremes you should avoid. Never let the edge of the mounting bracket extend below the bottom of the hull. Never let the bottom – the face – of the transducer rise above the bottom of the hull.

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 installa- tion (often called "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 opera- tion and good to excellent depth capability.

There is no possibility of damage from floating objects. It can't be knocked off when docking or loading on the 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. This can be a problem 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, a Skimmer transducer with a built-in temp sensor will show only the temperature of the bilge, not the water surface temp.

Follow the procedure 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.

1.Assembling the bracket. Press the two small plastic ratchets into the sides of the metal bracket as shown in the following illustration. Notice there are letters molded into each ratchet.