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Mounting a transducer for a depth finder

D

dhyams

Regular Contributor
"I'm just looking for opin

"I'm just looking for opinions on how I should mount a new depthfinder/fishfinder that I bought. I don't care about finding fish (this is a ski boat); I just want a reliable depth finder.

Anyway, this is a low-end fishfinder, with a mount that is more for a transom (external) application than it is a shoot-through-hull (it looks like a streamlined bulb rather than a hockey puck). It can, according to the instructions, be stuck down inside the hull, though.

I was just wondering if I should transom-mount it, drilling a hole through the transom to pass the wire, OR glue it down in the bilge with some below-waterline marine silicone. I don't want to use the epoxy for fear of not being able to move the transducer in case it's in the wrong place.

Anyway, just looking for any advice that anyone is willing to give ;)"
 
"Daniel...

I'm just abo

"Daniel...

I'm just about in the same boat as you. I'm also in the middle of putting a depth alarm in my boat. Again not for finding fish, but rather for finding (avoiding) rocks. I've been thinking about the whole thru the hull or external on the transom thing too. Epoxying it inside the hull has a few problems for me as its very difficult to see or have access to the area under my oil pan to try and epoxy one on. You have to make a mould to set the tranducer into while the epoxy sets up. I've been told that a section of 2 liter plastic pop bottle will work well for this. The expoy needs to be bubble free when it has set up or the transducer may not work properly. I think I'm just going to go with the external one on the transom. I'll sneek the wire out the back thru an existing hole somewhere or possibly make a hole high up under my swim platform , but that will be as a last resort. I'm thinking about using a piece of thin stainless steel angle and drilling mounting holes in it to match the holes in the bulkhead fitting that has the garboard plug in it. Die grind/drill a large hole in the center of the angle to accomodate the plug itself. Then screw it on over the plug. No other holes need to be drilled to fasten the transducer to the transom. Attach the transducer to the angle and it will be right at the lowest part of the hull.

I'm still thinking on all of this as well.

Wrench"
 
"I had the external one mounte

"I had the external one mounted on the transom and it is fine. 2 small holes for screws and one for the wire.

Have also heard that you can place them in the bilge, flat down and they will work fine. Good option for someone that doesn't feel right about drilling."
 
"Daniel...

Here is a copy o

"Daniel...

Here is a copy of a thread that I started awhile back. There maybe something in it for you as well......


Posted on Wednesday, March 19, 2008 - 07:06 pm:

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Hi guys....

I just got back home from a trip to NY state. (Just discovered Gander Mtn. down there. We deffinately need that store up here. Guy G., I bought some Sea Foam there on your recomendation. $6.99 / pint. Is that good?)

The guy at Bass Pro in Toronto said that when they install a depth alarm with an in hull transducer, they use a bunch of 2 part epoxy and make a little mold out of a plastic pop bottle. They put the transducer in the mold and fill it to the top with the epoxy, covering the transducer completely and gluing it down to the hull. ==== The guy at the Bass Pro in Auburn NY. didn't think that the above method was very good and that I should go with an externally mounted transducer on the transom. (thats what they do) He also mentioned that when the in hull transducer is mounted at the factory, they thin out the hull a little where it will be glued down so it will read better going through thinner fiberglass. (??????). I would prefer to go with the in hull one just to keep the back of the boat cleaner, but can't even see the the floor under my 4.3 I'm not too hip on the idea of drilling holes in the back of my boat, even though I have an externally mounted one on the back of my old ski boat for 20 years now with no gell coat problems... but that is my old boat, not my good boat... Anyone have any ideas about this or have any ideas as to what they have done in the past when putting theirs in? I want to get going on this as soon as it comes out of storage.

Thanks

Wrench


Bt Doctur
Advanced Member
Username: bt_doctur

Post Number: 131
Registered: 06-2006
Posted on Wednesday, March 19, 2008 - 07:40 pm:

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the trick i have used when drilling external holes in a boat where there is wood is to locate the item first,drill the hole to the proper diameter,mix up some resin and fill this hole completely first,(it soakes into the exposed wood), redrill and insert a hardwood dowel coated in resin,them mount the item using a sealant on the bolts/screws.


Guy Gaspar
Senior Member
Username: guyjg

Post Number: 1741
Registered: 08-2006
Posted on Wednesday, March 19, 2008 - 09:53 pm:

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Wrench:

$6.99 is about what I pay in SW Ohio, USA.

The trouble with installing transducers inside the hull is the installer and the prep work. If the hull is SOLID fiberglass and not the new sandwich fiberglass that has a honeycomb core, the transducer will shoot thru the hull and return a good echo.

I replaced my thru hull transducer last year. I chipped the old one off of the hull w/a wide wood chisel and then used a 50 grit 5" sanding disk to clean off all the old epoxy and remove some of the fiberglasss from inside the hull--1/8". You can use a cutoff wheel.

I installed a base filled w/mineral oil to the hull and then inserted the transducer into the base; it works perfect w/the new Faria gauge.

If you use epoxy the manner of mixing the epoxy is extremely important. The epoxy mix cannot have any bubbles in it that will interfere w/the transmission of signals. Prep your hull first and clean the area and transducer w/brake cleaner. Use plumbers putty to make a thumb size donut about 1/4" - 3/8" wider in diameter than the transducer. Place the putty donut on the hull floor where you want it. DO NOT
MOVE the donut because it has an oil base and the epoxy won't stick where it was.

Mix enough epoxy to make a pond 1/8" - 1/4" deep in the donut--LESS IS BETTER. To mix epoxy w/out air bubbles: use a clean flat wood board (luan board works well) and place the epoxy in the center. DON'T STIR it. Use a 3" drywall tape knife to spread the mix onto the board. While turning the board 1/8th turn pick up some mix w/the knife, turn it over and smash the mixture onto the board and spread it a few inches. Continue doing this procedure until the mix is well blended. When the epoxy is well mixed, scrape the mix to the edge of the board and tilt the board and scrape enough mix into the donut mold. Now take the transducer and press it into the epoxy w/even pressure and w/o twisting it. Place a brick or heavy object on it to hold it in place until the epoxy is set or overnight. Remove the donut and its ready to go.

Bt Dr's method is one step better than mine; I haven't used a dowel before. I use EPOXY resin with some filler, saw dust flour or silica, to make a putty which won't ooze out; tape over it anyway."
 
"Posted on Monday, September 1

"Posted on Monday, September 15, 2008 - 09:03 pm:

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Rob: what did you use to seal the holes, and are there any tricks to that?

No tricks, used silicone, just make sure you don't drill the holes larger than you need and fill with the sealant and put some on the screws when you insert, then check every now and then."
 
"There is a waaaay simpler, ch

"There is a waaaay simpler, cheaper way to do this, i.e., shoot thru the hull. I can't claim credit for the original idea, as I found it in a long forgotten post on the internet some years ago. I did "perfect" the procedure since as stated the original solution had some problems.
I presently use this method with a dual beam fishfinder (Humminbird Matrix ) and it works just fine (third season), shooting thru the very bottom of a Deep V (non cored) Hull (1969 23 ft ChrisCraft Lancer)

Materials and tools:
Block of "Duct Seal" (Home Depot or your favorite other store)
Mineral Spirits (to clean inside of hull)
Paper towels
One pair disposable gloves
Coarse sandpaper
Sharp, sturdy knife (a box cutter will work)
piece of Aluminum foil

Best done on a warm sunny day...

1) Find spot in hull where you want to mount transducer.
2) Remove duct seal block from wrapper and wrap it in aluminum foil tightly. Put it in a sunny spot to soften slightly.
3) Have lunch
4) Clean spot in hull (at least 4x4 inches) VERY VERY well with mineral spirits and use sandpaper to remove any fiberglass bits that may be sticking up. Clean again. Wait for Mineral Spirits to dry. Wipe away any residue.
5) Remove block from foil
6) Cut block in half (across the narrow dimension).
7) Carefully trim off about 1/4 inch off of the other five surfaces of the block (block tends to form a skin that causes problem, you should see a non-shiny surface on all six sides).
8) Form the block into a sphere with a smooth surface (wear disposable rubber gloves if your hands are the least bit dirty or oily to do this...very important!)
9) Place duct seal sphere into hull in desired location.
10) Locate transducer (make sure its clean and oil free!) on top of sphere. Some transducers have a fore and aft, make sure you are correct.
11) Slowly and with a fair amount of force, press the transducer down until the duct seal sphere deforms and conforms to the hull and also wraps around the full active face of the transducer. When done the top surface will be somewhat "dished".
12) Test Sonar.
13) IF satisfied, you can now carefully press the outer edges of the duct seal block where it contacts the hull so that it meets the hull at a shallow angle. Pressing the block down initially leaves the block with a negative angle all around at the hull that can trap water and freeze.

If there is any skin on the duct seal or oil on the hull or on the transducer or your hands, it won't work. Its removeable at any time with no tools."
 
"Hmm, I looked at both Lowes a

"Hmm, I looked at both Lowes and Home Depot for Duct Seal, and couldn't find any (they had the kind that comes in a plastic tub, but that stuff looked way too thin).

So I'm trying just regular plumber's putty. I figure if it doesn't work, I haven't lost anything except for the time it takes to remove the rear seat such that I can reach the bilge."
 
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