Through hull or transom mount transducer?

[chrisclin]

Having followed the instructions to use a waterbag to find the right spot, I decided not to bother with oil. I therefore cut the bottom out of a margarine tub and sikaflexed it to the hull forward of the keels and near the centreline. I then added water and placed the transducer in it. I cut a slot in the lid for the cable.
It has worked fine from grounded at low tide to over 70 metres - the deepest I've been in so far. And it's carried on working on a hard beat to windward in wind over tide conditions.

 

[ianfr]

Some years ago, I bought a Raymarine plotter, with fishfinder. It came with a transom mount transducer. I hacksawed the mounting bits off it, and installed it inside the hull on epoxy. Works perfectly.

Ditto here, but the transducer is held on butyl tape.

 

[BrianH]

I too have had total success mounting a transom mount tranducer inside a hull on 3 different boats. The first I followed the wisdom of the time, 20 years ago and fitted it in a tube of castor (?) oil the following two boats I just used a bit of gelcoat filler on one and on the other i used epoxy. Both worked perfectly but I would not go down the epoxy route as when I came to remove the transducer it brought away a bit of the layup with it. So a rigid adhesive but not too good a bond! As has been mentioned Sikaflex is also good.

I have just replaced my ancient and fading screen fishfinder with a Lowrence Hook 4x - not because I want to find fish but because it is a cheap and highly functional sonar depth instrument to not only see a clear depth reading but for a graphical display of the bottom - and I have plenty of mounting real-estate on my dog-house navigation table for the removable display.

I too did not want to epoxy the transducer into the bilge having experienced how difficult it was to remove the old one. Instead a wodge of transparent silicone with the transducer pressed down firmly into it with a temporary weight on top sufficed; the hardened silicone block now holds the transducer firmly but could be cut away if relocation is needed. No need for that yet as, so far, it functions perfectly.

 

[M33]

I too have had no problem mounting a transducer to fire through the hull. I experimented by building a coffer dam round the transducer with plasticene, filling the middle with water and pressing the transducer into the puddle. Worked so well, I cut the bottom out of a margarine tub, epoxied the skeleton to the bilge and put some cooking oil in followed by the transducer and it worked fine for 5 years til I sold the boat. That was on a Westerly where the hull was inches thick and the sounder didn't run out of puff until it was over 200 metres deep.
One problem I was trying to avoid was seeing how deep the bit was I'd just gone over - I prefer to have the transducer as far forward as possible.

The previous owner of my boat obviously worked on the theory of mounting it as far forward as possible as well. The trouble I am having is as soon as the weather cuts up rough as the transducer stops working as it spends a lot of time out of the water. Did you not suffer with this problem as I am thinking of moving mine further aft so it is always in the water. I don't think 1m or so of warning is really enough for me to react anyway.