# SILICONE to mount in-hull transducer?



## dixiedawg (Sep 22, 2013)

_Silicone??
_
That's what my instructions are saying, to use clear silicone! I had always heard they were epoxied in place, but the instructions say something about this way being better because it's removable. (The PO was very much in love with clear silicone, and used it ALL OVER my boat, and every time I find myself sanding it off I want to go find him and wring his bloody neck).

BTW, the instructions also go on to recommend glycol to fill the unit, which is something else I wouldn't have expected. Are they talking ordinary antifreeze?

As I am a sailboat neophyte, I appreciate any words of wisdom, thanks!


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## ReefMagnet (May 8, 2008)

Is this to shoot through a solid f/g hull? In that case silicon will work perfectly with the following caveats; 1) make sure the transducer gets a clear reading through the hull at the desired mount location BEFORE mounting it permanently in place. KY jelly or vaseline makes a great temporary medium for this and 2) don't allow any air bubbles to form in the silicon during the installation process.


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## Delezynski (Sep 27, 2013)

Dixie,

You might want to take a look at one of the projects web pages. It's at;
Guenevere's Projects, Depth sounder
and shows how we did a no hole depth gauge on our boat.

Greg


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## jrd22 (Nov 14, 2000)

I've mounted several in hull transducers using silicone and it works great. I used a zip lock bag with mineral oil in it to locate a good location on the hull, then apply a large blob (technical term) of clear silicone. Hold the tip of the tube in the center of the location you've chosen and just squeeze it out around the tip, that results in the fewest bubbles forming. Just let the ducer settle down into it (angle it a bit at first to let air escape) and secure it with duct tape or something if it tends to move downhill on you.


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## mitiempo (Sep 19, 2008)

I have installed one with silicone and many using epoxy which is recommended by most depth sounder manufacturers. Epoxy is the best in my opinion, bubbles aren't an issue. There is no real need to make it removable.

To find a good location I just place the transducer in a baggie of water and move it around until it works.

Here is a link to West Epoxy's instructions to install a transducer.

WEST SYSTEM | Modifying and Customizing Boats - Depth sounder installation


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## Delezynski (Sep 27, 2013)

mitiempo said:


> I have installed one with silicone and many using epoxy which is recommended by most depth sounder manufacturers. Epoxy is the best in my opinion, bubbles aren't an issue. There is no real need to make it removable.
> 
> To find a good location I just place the transducer in a baggie of water and move it around until it works.
> 
> ...


mitiempo,

I don't mean to be contrary, but the statement, "There is no real need to make it removable." sounds like some one who has never purchased a used boat, or owned a boat for more than a few years. EVERYTHING always needs to be replaced at some time or another!

I guess I am just a geezer. 

Greg


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## mitiempo (Sep 19, 2008)

It is removable, but not to re-use. A good whack with a hammer sideways will remove it. No reason to if it is working though.


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## Capt Len (Oct 9, 2011)

There are few things on a boat that a good whack with a hammer won't set right.


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## Delezynski (Sep 27, 2013)

Capt Len said:


> There are few things on a boat that a good whack with a hammer won't set right.


 ..................

..........
Or the proper application of the correct amount of explosive! 

Greg


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## dixiedawg (Sep 22, 2013)

Delezynski said:


> Dixie,
> 
> You might want to take a look at one of the projects web pages. It's at;
> Guenevere's Projects, Depth sounder
> ...


Greg, that's essentially how my transducer (Airmar P79) mounts. It comes with a plastic cylinder "base", which is cut at an angle and flanged on one end. This end is placed on the hull, rotated until the top end is perfectly level, and siliconed down. After curing, it gets filled with propylene glycol and the 'ducer gets sealed inside.

I'm still surprised at the use of clear silicone, but if it worked for you, I'm sure it'll work for me! And I might very well have to move the 'ducer, since I was unable to test it with the boat in the water prior to mounting. I have it placed in the area recommended by Airmar, and where other owners of Catalina 22's have mounted theirs, so I hope my odds of success are at least pretty fair.

I'm not sure why Airmar recommends the propylene glycol, either, but I'll just roll with it. After some research, I've found Prestone "Lo-Tox" antifreeze uses propylene glycol in a concentration of 90-100%, according to their MSDS's. So, it's off to the auto parts store in the AM.


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## mitiempo (Sep 19, 2008)

dixiedawg said:


> I'm not sure why Airmar recommends the propylene glycol.....


So it doesn't freeze and crack the tube or damage the transducer.

This was more common in the past than now. I have had several boats with the transducer in fluid filled tubes. On my current boat it was done this way and the fluid had all leaked out. It was aft, wrong place anyway.

Most depth sounder manufacturers recommend epoxy now as I posted, a few silicone, but rarely do they recommend the fluid filled tube - just attaching the transducer directly to the inside of the hull is the easiest and most maintenance free way.


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## dixiedawg (Sep 22, 2013)

mitiempo said:


> So it doesn't freeze and crack the tube or damage the transducer.


Ah, yes, of course. Too many years in Florida makes you forget such things.


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## Delezynski (Sep 27, 2013)

dixiedawg said:


> I'm not sure why Airmar recommends the propylene glycol, either, but I'll just roll with it. After some research, I've found Prestone "Lo-Tox" antifreeze uses propylene glycol in a concentration of 90-100%, according to their MSDS's. So, it's off to the auto parts store in the AM.


Good luck and hope it works first time for you!

I used mineral oil and it's been working for many years. BUT, we are in warm to tropical waters ALL of the time.... 

Most likely they recommend the poly-gly in case the craft is in a cold climate. If I was in an area where it drops below freezing, I would most likely go that way.

POST PHOTOS!

Greg


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## Missingyou (Aug 16, 2013)

If I remember the recommendations for my P79
indicated that epoxy will become brittle over time, which would lead to leaking. I used 3M 4200 as it was what I had handy. I've since heard that some adhesives may attack the plastic, not sure if 4200 will. Silicone is probably a safer bet. 

The Propylene Glycol of course makes sense for reasons of freezing. I took a chance and mounted it permanently without testing function and it works great. I do know that it will not work without being filled with liquid. I also applied a food grade lubricant to the threads as I do with my strainer basket lids.


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## mitiempo (Sep 19, 2008)

Missingyou said:


> If I remember the recommendations for my P79
> indicated that epoxy will become brittle over time, which would lead to leaking.


Polyester gets brittle - epoxy shouldn't.

The transducers are potted in epoxy - nothing will have an effect on it.

That is the beauty of attaching the transducer to the hull with whatever you choose instead of a liquid filled tube - nothing to leak.


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## Missingyou (Aug 16, 2013)

mitiempo said:


> Polyester gets brittle - epoxy shouldn't.
> 
> The transducers are potted in epoxy - nothing will have an effect on it.
> 
> That is the beauty of attaching the transducer to the hull with whatever you choose instead of a liquid filled tube - nothing to leak.


The instructions state that epoxy is too brittle. Here are the Warnings within the Installation Instructions.

WARNING
: Always wear safety goggles and a dust
mask to avoid personal injury.
CAUTION
: The fiberglass hull below the transducer
must be solid. The transducer
will not transmit through
coring material such as foam or balsa wood.
CAUTION
: Do not use an epoxy adhesive because it
is too brittle.
CAUTION
: Never pull, carry, or hold the transducer by
the cable. This may sever internal connections.
CAUTION
: Never use solvents. Cleaners, fuel,
sealants, paint, and other
products may contain strong
solvents, such as acetone, which attack many
plastics, greatly reducing their strength.
IMPORTANT
: Please read the inst
ructions completely
before proceeding with the installation. These
instructions supersede any ot
her instructions in your
instrument manual if they differ


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## Minnesail (Feb 19, 2013)

Capt Len said:


> There are few things on a boat that a good whack with a hammer won't set right.


In the computer maintenance field we refer to this as percussive maintenance, and if you want to sound more professional than "give it a thump" we say "it needs a technical tap."


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## mitiempo (Sep 19, 2008)

Missingyou said:


> The instructions state that epoxy is too brittle. Here are the Warnings within the Installation Instructions.


Epoxy is no more brittle than the polyester you are attaching it to. Having used epoxy for over 25 years (West System as well as other brands) I have never found it brittle. As I posted the transducer face can be epoxied to the hull without the tube and fluid. It has worked fine for my customers as well as on my own boats in every instance - for Airmar as well as other brands of transducers.


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## dixiedawg (Sep 22, 2013)

Brian, I was intrigued by the West System method in the link you posted, is that the way you get the unit perfectly level, without the use of an angled base of some kind?


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## mitiempo (Sep 19, 2008)

dixiedawg said:


> Brian, I was intrigued by the West System method in the link you posted, is that the way you get the unit perfectly level, without the use of an angled base of some kind?


Yes


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## Barquito (Dec 5, 2007)

In order to find a good spot on my C22, I stuck the transducer in a wad of toilet bowl mounting wax. I ended up leaving it there for 4 years, no problem. May not work so well in warmer areas of the country. My boat now has the transducer mounted in a pool of epoxy. However, there was some releasing agent between the epoxy and the hull (wax?), so it can be removed without any technical tapping. I would be a little worried about putting it in too big of a pool of epoxy. The epoxy get pretty hot while curing.


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## mitiempo (Sep 19, 2008)

Barquito said:


> In order to find a good spot on my C22, I stuck the transducer in a wad of toilet bowl mounting wax. I ended up leaving it there for 4 years, no problem. May not work so well in warmer areas of the country. My boat now has the transducer mounted in a pool of epoxy. However, there was some releasing agent between the epoxy and the hull (wax?), so it can be removed without any technical tapping. I would be a little worried about putting it in too big of a pool of epoxy. The epoxy get pretty hot while curing.


I avoid waxes as they can affect the epoxy (or silicone) sticking. I use a baggie of water and move it around until I get good results, best place being forward of the keel, usually under the aft end of the V-berth. A no mess solution. If the hull is V'ed and needs thicker epoxy I do it in stages to avoid heat.


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## Missingyou (Aug 16, 2013)

The West System method seems very slick. Wish I would have gone that route. I keep a can of Acetone and sandpaper onboard to clean surfaces before mounting anything. 

All in all I'm thankful the P79 exists. I didn't have to drill into the hull and the transducer works great in my application mounted forward of the keel. I did have to buy an extension cable. I didn't actually get it working until the last week of the season. It was fun seeing all of the fish in the Chesapeake and the C&D Canal in early November, a few of them big. I also installed two rod holders for next season.


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## SVTatia (May 7, 2007)

mitiempo said:


> ......best place being forward of the keel, usually under the aft end of the V-berth. A no mess solution. If the hull is V'ed and needs thicker epoxy I do it in stages to avoid heat.


Do you build any kind of a "wall" around the transducer to protect it from something banging into it? If so, how do you do it?

Could you cut a piece of PVC pipe conforming to the hull angle and a bit larger and a bit taller than the transducer, glue it using silicone then once set, pour the epoxy and stick the transducer inside, would that work?


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## Missingyou (Aug 16, 2013)

SVTatia said:


> Do you build any kind of a "wall" around the transducer to protect it from something banging into it? If so, how do you do it?
> 
> Could you cut a piece of PVC pipe conforming to the hull angle and a bit larger and a bit taller than the transducer, glue it using silicone then once set, pour the epoxy and stick the transducer inside, would that work?


Mine is not in a place of concern under the forward cabin floor but I suppose you could put something around it. How about a PVC water closet(toilet) flange?


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## mitiempo (Sep 19, 2008)

SVTatia said:


> Do you build any kind of a "wall" around the transducer to protect it from something banging into it? If so, how do you do it?
> 
> Could you cut a piece of PVC pipe conforming to the hull angle and a bit larger and a bit taller than the transducer, glue it using silicone then once set, pour the epoxy and stick the transducer inside, would that work?


Every boat and location is different. All you want is something to protect it from items stored in the locker. Whatever works in your location, but doesn't have to be a tube, just an effective guard of some sort if the transducer is exposed.


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## fryewe (Dec 4, 2004)

dixiedawg said:


> Greg, that's essentially how my transducer (Airmar P79) mounts. It comes with a plastic cylinder "base", which is cut at an angle and flanged on one end. This end is placed on the hull, rotated until the top end is perfectly level, and siliconed down. After curing, it gets filled with propylene glycol and the 'ducer gets sealed inside.
> 
> I'm still surprised at the use of clear silicone, but if it worked for you, I'm sure it'll work for me! And I might very well have to move the 'ducer, since I was unable to test it with the boat in the water prior to mounting. I have it placed in the area recommended by Airmar, and where other owners of Catalina 22's have mounted theirs, so I hope my odds of success are at least pretty fair.
> 
> I'm not sure why Airmar recommends the propylene glycol, either, but I'll just roll with it. After some research, I've found Prestone "Lo-Tox" antifreeze uses propylene glycol in a concentration of 90-100%, according to their MSDS's. So, it's off to the auto parts store in the AM.


My transducer installation was similar. The base provided is genius because it allows installation on an angle with no home engineering. I was able to mount mine on the centerline with a zero angle.

I cleaned the fiberglass at the mounting location with 60 grit wet/dry sandpaper then acetone. Then I mounted the base with Boatlife caulk. I filled the base with mineral oil (freezing point -22F). If my bilge is colder than that I got bigger problems than freezing and cracking the base of my depth sounder installation.

I am very happy with the result. Been in service a couple of years.


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## ltgoshen (Jan 5, 2009)

mitiempo said:


> I use a baggie of water and move it around until I get good results, best place being forward of the keel, usually under the aft end of the V-berth. A no mess solution. If the hull is V'ed and needs thicker epoxy I do it in stages to avoid heat.


I have a transducer there for depth and one apposing that one for a paddle-wheel for speed? all older st50 stuff. Wander if it will adversely effect its reading if I put in in the same vicinity?


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## ltgoshen (Jan 5, 2009)

jrd22 said:


> I've mounted several in hull transducers using silicone and it works great. I used a zip lock bag with mineral oil in it to locate a good location on the hull, then apply a large blob (technical term) of clear silicone. Hold the tip of the tube in the center of the location you've chosen and just squeeze it out around the tip, that results in the fewest bubbles forming. Just let the ducer settle down into it (angle it a bit at first to let air escape) and secure it with duct tape or something if it tends to move downhill on you.


How do you know when you have found a good location?


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## algee (Feb 28, 2010)

There is a product called Duct Seal Compound. It costs less than $5 at the big box hardware stores. I going to try it. Have any of you tried it?


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## mitiempo (Sep 19, 2008)

algee said:


> There is a product called Duct Seal Compound. It costs less than $5 at the big box hardware stores. I going to try it. Have any of you tried it?


Looks a bit like butyl. The more solids in the material used the less effective the depth sounder. Use silicone or epoxy.


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## Argyle38 (Oct 28, 2010)

For those that have installed the P79, can I ask how you rate the performance? I have a Raymarine DSM300 that I bought last year but haven't installed it yet. My choices for transducer is one of the through hull designs, the P79 or the much more expensive M260. 

I've always leaned toward an in-hull transducer since I have a solid glass hull. I have plenty of room for the larger M260, but at 5x the price over the P79 it seems like it might not be worth it for an extra 400W of power. 

So, do you like your P79's or do you wish you had more power?

Have you been able to compare to through-hull type transducers?

Also, what type of module and display to have it attached to?

-Argyle


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## jimgo (Sep 12, 2011)

Is there usually air trapped in the silicone in a tube?


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## mitiempo (Sep 19, 2008)

It's easy to get bubbles in silicone. That is one reason I use epoxy.


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## christian.hess (Sep 18, 2013)

Ill be doing this soon on a cheap garmin fishfinder....mounted in hull

Ill be going the mineral oil in a pvc tube cap way as it is completely "removable" jajaja not that it needs to be...learned this trick from you guys on here.

I hate clear silicone and anything remotely related to it like 5200 etc...much rather use manual methods

Ill post an update next year! jaja

cheers


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## christian.hess (Sep 18, 2013)

never understood why people want more power out of their depthfinders..what you need is the perfect spot to mount it perfectly upright so it shoots a clear uncorrupted line down to the bottom...

more power will only give your more ability to see larger depths...not what you need a depthsounder for

or is there more to it? my studies have shown me to look more at proper installment over "power"


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