Depth Transducer Fitting - what do we know?

[Ribtecer]

So in my Rib rebuild I am wanting to fit a depth gauge.

I have bought a Lowrance hook 4 as it gives me GPS speed/location and depth, not interested in finding fish.

The depth transducer can be mounted on the exterior of the transom (messy, vulnerable and ugly) or it can be fitted to the inside of the hull.

The instructions say bed it in epoxy, I have heard before to bed it in silicone, which is best? Any other help/advice much appreciated. (My preference is silicone as, if required at any point, it can be removed much easier without the risk of breaking the plastic housing.

Much obliged.

 

[matthewriches]

I use “plastic padding” a lot which comes in 2 tubes that you mix together. Resembles car body filler. Otherwise expoxy.

 

[salar]

If you want to be able to remove the transducer from an inside-hull mounting position you can buy a foam mount kit, or for much less money make your own. Here's how I did it and it is much more protected than a bare transducer: https://harley25refit.blogspot.com/2018/05/a-fish-finder-for-cockpit.html

 

[John the kiwi]

8 years ago i bedded the transducer into a lump of petroleum jelly on the inside of my glass/plywood hull, to see if it would work.
It did and it was so firmly bedded that I simply covered it with a small inverted box to avoid knocks and left it.
I was worried that in summer the vaseline may soften and release the transducer, but that hasn't happened - its been totally reliable.
Best of all i could pull it out and replace it using nothing more than a cloth to wipe it down if i needed to.
Try doing that with something epoxied or siliconed into place!

 

[Daydream believer]

Are you worried about small leaks in a RIB? If not then on flexible bedding or just a neoprene washer. I would suggest that it may need to be easily removable as it could get trailer damage if launched & recovered a lot. Our club safety boats take a lot of abuse to the hulls. Even quite protected parts ( ie next to ribbing) get sand & trailer wheel abrasion. Being privately owned yours will be, presumably, less abused; it depends on how & where you intend to use it. The transducer may get some damage over time. Not sure how much "inbuilt" protection they have on the face.

 

[Tranona]

Are you worried about small leaks in a RIB? If not then on flexible bedding or just a neoprene washer. I would suggest that it may need to be easily removable as it could get trailer damage if launched & recovered a lot. Our club safety boats take a lot of abuse to the hulls. Even quite protected parts ( ie next to ribbing) get sand & trailer wheel abrasion. Being privately owned yours will be, presumably, less abused; it depends on how & where you intend to use it. The transducer may get some damage over time. Not sure how much "inbuilt" protection they have on the face.

From what the OP says he is mounting it inside the hull rather than through the hull so none of that is relevant - and perhaps why in hull mounting is the preferred method.

 

[Ribtecer]

^^^ As he says, inside the hull.

Many thanks.

 

[PaulRainbow]

The correct method for fitting in hull is to use slow drying epoxy. There will be those that state theirs are stuck in with Silicone, but the transducer manufacturers explicitly state this should not be used. The method in post #3 would also be acceptable.

 

[Ribtecer]

Many thank PaulRainbow for a straightforward definitive answer.

Much appreciated.

Last what exactly is "slow drying epoxy" and who supplies it please.

 

[PaulRainbow]

Many thank PaulRainbow for a straightforward definitive answer.

Much appreciated.

Last what exactly is "slow drying epoxy" and who supplies it please.

You could just use some Araldite.

 

[BarneysDad]

The correct method for fitting in hull is to use slow drying epoxy. There will be those that state theirs are stuck in with Silicone, but the transducer manufacturers explicitly state this should not be used. The method in post #3 would also be acceptable.

I've read this many times "silicone should never be allowed near a boat". As my silicone embedded yacht windows dropped out, I'd go along with that .

 

[simonfraser]

i'd def not stick something that is likely to break down with a permanent adhesive.
have used silicone inside the hull, without drilling a hole b4 without a problem.

 

[PaulRainbow]

i'd def not stick something that is likely to break down with a permanent adhesive.
have used silicone inside the hull, without drilling a hole b4 without a problem.

Even though the people who manufacture the transducers explicitly say not to use silicone, use epoxy ?

How well do you suppose sound waves travel through silicone sealant ?

It's easy enough to remove the transducer, if it should ever need removing.

 

[pvb]

It's easy enough to remove the transducer, if it should ever need removing.

If it ever needs removing, it's probably broken anyway.

 

[simonfraser]

Even though the people who manufacture the transducers explicitly say not to use silicone, use epoxy ?

How well do you suppose sound waves travel through silicone sealant ?

It's easy enough to remove the transducer, if it should ever need removing.

travels very well in my past experience, just don't want air bubbles in it.

 

[PaulRainbow]

Another benefit of doing the job correctly is that you can correct for hull deadrise. Make a dam with Plasticine or similar, a little larger in diameter than the transducer and deep enough so that it will hold enough epoxy to level out the hull deadrise. Pour in some slow drying epoxy until it's level, then leave to harden. As it's slow drying epoxy any air bubbles will be able to escape. When it's hard enough, add a small amount of epoxy and fit the transducer with a twisting motion to dispel any air.

Job done. The transducer will be facing directly downwards. Should it fail and need removal, use a thin chisel or a knock through screwdriver, hold it against where the transducer face joins the epoxy and give it a sharp knock with a hammer. The transducer will come off cleanly and normally without any damage, in my experience.

 

[Bodach na mara]

I fitted mine (a transom mounting for a Garmin Fishfinder) inside my last boat with a large blob of silicon. Manufacturers were not saying anything against it at that time. The fix was still working perfectly 16 years later. In fact it worked better than the depth meter, with a through-hull transducer, which rarely gave a reading of the depth was over 60 feet. The fishfinder always worked to depths up to 250 feet and in good conditions it gave readings to about 350 feet.