Transducer location

[king5899]

I was told on an inboard boat you need to install a thru-hull transducer as opposed to a transom mount. Is there any reasoning behind this? I was thinking of a transom mount mounted between my 2 prop tunnels, next to the drain plug. this way I don't have a hole going through the hull, just a couple of screws.

Anyone have any input on this one?

MJK

 

[cmariner32]

No reason why you can't use a transom mount. I've got inboards with a transom mount and have no problems. You do have to watch where you install it as you need clean water-i.e. no bubbles or prop wash which could interfere with the signal.

 

[boatpoker]

The disturbed water at the transom will quite likely confuse the transducer. There is no need to drill a hole for a "shoot-thru" application in fact you can take the transom mount transducer and bond it to the hull in a bed of epoxy and it will work fine. Get a cardboard roll like from a roll of duct tape, tape it to the inside of the hull with waterproof tape, fill it with epoxy and then place the transducer in the epoxy. Make sure there are no bubbles in the epoxy.

The last fish/finder/depth sounder I bought was an Eagle unit with the transom mount transducer and the instructions also suggested this epoxy method which I have used with no problems.

the id4al location for the transducer is 100' in front of your boat

 

[king5899]

My boat has a cored hull so a shoot thru is out.

MJK

 

[Sandy]

There are 2 F/F's, each with it's own 50/200khz T/D, on my twin I/B with prop pockets. One has a mid-ships Ratheon/Airmar B-744V T/H w/ high-speed fairing block, and the other has a great Lowrance HST-50/200(?)(speed paddle is seperate unit also installed) transom-mount Skimmer mounted on the centerline. Both work well but the Lowrance T/M Skimmer works much better at cruise speed of 22-26kts with rarely any noise.

It may be that the prop pockets help redirect the upper prop wash a bit more directly aft to help T/d results, and the design of the particular T/M T/D would be a factor, but if you cave to "conventional wisdom" that T/M 's are not for I/B's you may be depriving yourself of great results like mine.

 

[seahawk215]

You could take out a small section of the core from inside and do it this way. Probably the best way to go.

http://airmartechnology.com/uploads/installguide/17-217-01.pdf

Installation in a Cored Fiberglass Hull
Installation in a cored hull is difficult. The objective is to bond the
base to the inside surface of the hull’s outer skin while
preventing any moisture from penetrating the core.
CAUTION: There is no way to determine if the outer skin is solid
(no trapped air bubbles in the fiberglass) at the selected location
before cutting the inner skin.
WARNING: Always wear safety goggles and a dust mask.
1. Using a 100mm or 4" hole saw, cut through the inner skin and
the core at the selected location (see Figure 9). The core
material can be very soft. Apply only light pressure to the hole
saw after cutting through the inner skin to avoid accidentally
cutting the outer hull.
2. Remove the plug of core material, so the inner core of the hull is
fully exposed. Sand the inside surface of the outer skin using
a miniature disk sander. Slightly undercut the surrounding
coring if possible.
3. Clean and dry both the inside surface of the outer skin and
the transducer with a weak solvent, such as alcohol, to remove
any dust, grease, or oil.
4. Place the base in the cavity. Fill the gap between the base and
the hull with casting epoxy or resin following the manufacturer’s
directions for its use.
5. After the casting epoxy or resin has cured, proceed with Installation”, on page 3.

 

[vic33004]

it depends on the power of the transducer. if you are simply looking for depth reading in relatively shallow water and an easy install the transom mount will do. the thru hull is generally considered a better installation and is the only way to go if you are using a more powerfull transmiter. the transducer is generally located forward of the prop tunnels in undisturbed water. if its a large transducer you'll also need a fairing block and a qualified installer is a good idea at that point. if you do go with the thru hull and you have core, be sure to seal the core with either resin or 5200 before installing the transducer.