Transom mount transducer inside hull.

[greycaster]

I am about to install a depth sounder with a transom mount. I have heard that it is possible to mount a transom transducer inside the hull and still get accurate results. I would be interested to hear from anybody who has mounted a transom transducer inside the hull.

 

[omega2]

yes we have, hang the transducer over the side of the boat in contact with the water, switch on and note the signal strength this will be the optimum, then chose a place 2/3rds along the boats length, place the transducer in a plastic bag with a little water in, plonk it around to get the best signal return that compares with the outside test. When "happy" lightly sand the area, and with a slow curing epoxy glue, gently squirm the face of the transducer onto the hull, this action will eject any air pockets. Or build a dam big enough to accept the transducer and fill with castor or baby oil then place the transducer into it. Will not work if your hull is a sandwich construction.

 

[VicS]

yes we have, hang the transducer over the side of the boat in contact with the water, switch on and note the signal strength this will be the optimum, then chose a place 2/3rds along the boats length, place the transducer in a plastic bag with a little water in, plonk it around to get the best signal return that compares with the outside test. When "happy" lightly sand the area, and with a slow curing epoxy glue, gently squirm the face of the transducer onto the hull, this action will eject any air pockets. Or build a dam big enough to accept the transducer and fill with castor or baby oil then place the transducer into it. Will not work if your hull is a sandwich construction.

A silicone sealant will make a less permanent fixing than epoxy. Important however you do it to ensure no air bubbles are trapped.

 

[gjgm]

A silicone sealant will make a less permanent fixing than epoxy. Important however you do it to ensure no air bubbles are trapped.

So dont use Araldite Rapid
Main problem with epoxies are they are so runny, and the hull usually isnt flat.You need to make some sort of plasticine bath to keep the epoxy in place til it goes off, or it all runs away.

 

[iainbluk]

transom mounted transducer in hull

I am afraid I was a bit lazy when I mounted my airmar depth transducer for the fishfinder part of my raymarine plotter..I just stuck it to the hull using builders non hardeneing mastic (like plasticine or blue tack) and there it has stayed for 7 years.....

Seems to show the depth just fine, although I have to admit to not catching too many fish ( a few though)

 

[beyondtheblue]

I used a Tupperware container with most of the bottom cut out, stuck it down with silicone, fixed the transducer to the side of container, fill with cooking oil, cut a notch in the lid for the cable

 

[noelex]

PVC water / drain pipe works well.

 

[yoda]

I've done it with a Navman transom transducer without any problem. Go for it.

Yoda

 

[Bodach na mara]

I used walpaper paste as a coupling agent to find a good bit of hull. then cleaned it off, dried it thoroughly and stuck the sensor down with silicon. I can get readings up to 300 feet.

 

[Norman_E]

I stuck a Navman one in with Blutack, just to test it you understand, and five years later it is still stuck in with Blutack and still works. It reads depth down to a little over 20 metres stuck that way, which is fine for a backup system.

 

[m1nder]

Why are some of you placing the transducers in liquid? Is that necessary?

 

[john_morris_uk]

Why are some of you placing the transducers in liquid? Is that necessary?

Its one way to get a 'perfect' contact between transducer and hull. Sticking it down with mastic or silicon achieves the same end result: good physical contact between the transducer and the hull to transmit and receive the ultrasonic sound waves.

Years ago, internally mounted transducers used to be fitted in tubes filled with some sort of oil. I remember a boat I was teaching on once used washing up liquid (which is obviously not an oil!)

 

[john_morris_uk]

Will not work if your hull is a sandwich construction.

I think you will find that very few hulls are built with sandwich construction below the water line. Years ago it was discovered lead to all sorts of problems and most manufacturers have avoided it for a while. Good point to watch out for if the OP has a one off or fancy racy boat though.

 

[Panache2010]

Silly question time, would this work on a marine ply hull?

 

[john_morris_uk]

Silly question time, would this work on a marine ply hull?

No such thing as a silly question - and the answer is 'yes' it will work on a marine ply hull ; just experiment a bit to find the best location.

 

[noelex]

Silly question time, would this work on a marine ply hull?

I think the results are typically very poor on wood hulls

 

[john_morris_uk]

I think the results are typically very poor on wood hulls

On more heavily built carvel type hulls that might be true - but I have seen depth transducers working through ply ok.

Despite this, I have always drilled a hole and mounted the transducer as per the manufacturers instructions - with the transmitting and receiving face in direct contact with the water.