Attaching transducer to transom with epoxy?

barrynfla

Petty Officer 3rd Class
Joined
Nov 3, 2012
Messages
81
I had a real leaky jon boat with a bad transom. I suppose I now have a phobia against putting any holes in the transom of my 13' fiberglass tri-hull.

I do want a fish finder and want to mount the transducer on the transom. I don't want to use the trolling motor as a mount and I don't want to mount it inside the hull since I want the temp reading. Does anyone know if marine epoxy will hold the transducer mount on the transom? Is this possible at all?

Thanks,

Barry
 

Augoose

Lieutenant Junior Grade
Joined
Mar 21, 2010
Messages
1,220
Re: Attaching transducer to transom with epoxy?

Yes it will - I used loctite marine epoxy and it worked great. My suggestion is this:
Pick up a cheap poly cutting board from walmart or somewhere else. Cut two, 2"x 2" squares (or whatever size square will marry up with the outline of your tranducer mount) and stack them together. Glue the two pieces together with the epoxy and then use the SS screws which came with the transducer mount to screw the mount into the poly board stack you made. Then roughen up the mating surface of the poly board along with the gel coat on the transom where you intend to mount the transducer. I then took a grinder and made a bunch of cuts in the mating surface of the poly board, about an 1" long by a 1/16" of an inch wide, to give the epoxy a better bonding surface vs a perfectly smooth surface with no depth.
Glue the whole thing onto the transom and give it several days to bond!
There are also commercial glue on mounts you can buy but they seem to be based on the same idea as above.
Good luck.
 

Auger01

Petty Officer 1st Class
Joined
Aug 15, 2009
Messages
201
Re: Attaching transducer to transom with epoxy?

I dislike holes in the transom as much as anybody. They are potential leak and or rot starters, but the following method guarentees no water intrusion. Drill 1/2" holes about 1" deep into the transom centered on where the screws would go into the transom. Mix up some epoxy PB (epoxy plus cabosil or woodflour or microballons) and fill the holes you just drilled. Filling the holes from the inside out with a empty caulk tube filled with your PB works best. Screw the transducer into the PB using 3/4 inch long screws and you are done.
 

64osby

Admiral
Joined
Jul 28, 2009
Messages
6,799
Re: Attaching transducer to transom with epoxy?

On my little tinny I mounted the transducer without more holes in the transom. This was my solution, an old piece of drawer slide material cut to fit. Mounts with one bolt at the top of the transom in an existing hole. Very sturdy and will not move, I tried.

LSTransducerMount.jpg
 

Yacht Dr.

Vice Admiral
Joined
Feb 26, 2005
Messages
5,581
Re: Attaching transducer to transom with epoxy?

If you mount the ducer plate properly with 5200 ( I prefer the fast cure 5200 ) I doubt you would have any problems.

Here is how I would do it without the epoxy mounting.

1. Install the ducer Dry ( without any 5200 ).
2. Tape the transom around the plate.
3. Remove the ducer.
4. Prep the area inside the tape lines with a scotch bright or 180(ish) sand paper.
5. Prep the ducer plate the same way. Give a few scrubs across where the screw holes are on the outside.
6. Acetone wipe both surfaces.
7. Apply a dab of 5200 FC on each hole.
8. Apply some 5200 FC on the mounting plate of the ducer. ( this is the trick .. smear the 5200 on the whole plate with a spreader or your latex gloved finger making a good 1/8" thickness of 5200 on the whole surface )
9. Hand Mount your ducer with a screwdriver .. only semi hand tight ! ( dont crank it down all the way ).
10. Clean up the gooshed 5200 with a flat head screwdriver.
11. Pull your tape.
12. Clean up any residual 5200 with a quick wipe of a dry rag .. then clean up the rest with a damp mineral spirit rag. Dont get too nutso cleaning up around the screw heads.

Now you have one of the best mounting gaskets. Some make the mistake of tightening the screws all the way down basically leaving No caulk between the two surfaces.

I see the Theory of Auger01s post. But without proper beading its still going to fail. Sure the screws/holes cant come in contact with the wood .. but the epoxy holes can.

If your still worried about screws into your transom .. then the best bet would be to lam glass a block of solid glass and epoxy that to your transom .. then mount the ducer to that.

Just get some wax paper .. cut up some mat and 1708 or woving roving. Wet out and roll till you you build up 3/4" of solid glass. Cut/sand that for your mounting plate. We used to make solid backing plates from left over resin/glass on the side. Basically if you had extra glass and resin about to kick .. you goto the Plate and use the left overs creating a 3/4" solid glass plate ( cut a section out when you need it ).

I hope this helps you.

YD.
 

ricohman

Lieutenant Commander
Joined
Jul 30, 2011
Messages
1,631
Re: Attaching transducer to transom with epoxy?

I used a Stern Mate mount kit on my new boat. Its glued on with the adhesive it comes with and the transducer bolts the mount.
It works great and allows to reposition as needed. And I am with you on not wanted to drill more holes than needed.
DSC04517.jpg
 

Auger01

Petty Officer 1st Class
Joined
Aug 15, 2009
Messages
201
Re: Attaching transducer to transom with epoxy?

I see the Theory of Auger01s post. But without proper beading its still going to fail. Sure the screws/holes cant come in contact with the wood .. but the epoxy holes can.


YD.

If done correctly, the epoxy should bond with the fiberglass skin of the transom and keep the water out. Most transom skins are at least 3/16 thick and that is penty of glass for the expoxy to bond to.

I agree that glueing a block to the transom and then scewing the unit to that is the most bulletproof option, but it may not be asthetically pleasing to some.
 

smokeonthewater

Fleet Admiral
Joined
Dec 3, 2009
Messages
9,838
Re: Attaching transducer to transom with epoxy?

If done correctly, the epoxy should bond with the fiberglass skin of the transom and keep the water out. Most transom skins are at least 3/16 thick and that is plenty of glass for the epoxy to bond to.

I agree that gluing a block to the transom and then screwing the unit to that is the most bulletproof option, but it may not be aesthetically pleasing to some.

I'd say that your method would be very likely to crack and leak... I would think that simply sealing screw holes with 5200 would be much safer.

Honestly, as tough as 5200 is you could probably just sand both surfaces and glue the 'ducer on with it. Secure with masking tape till it sets and it'll probably be there for good
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,588
Re: Attaching transducer to transom with epoxy?

Why not just install it inboard? I got tired of them getting damaged by water sports activities and fishing in timber. Moved inside ever sense and haven't looked back. Lots of how do do it on here.

Mark
 

Home Cookin'

Fleet Admiral
Joined
May 26, 2009
Messages
9,715
Re: Attaching transducer to transom with epoxy?

I agree with avoiding holes but also nothing on a boat lasts forever, so gluing equipment directly to the boat, or permanently gluing in screws, with inevitably give you problems down the road. Mounting a plate and then screwing into it is the best way.

Cheap cutting boardes eventually crack. I'd prefer wood over that, unless you have some starboard. remember wood doesn't rot because it gets wet; it rots if it stays wet. And if it does rot after 8-10 years, it's not a problem.
 

barrynfla

Petty Officer 3rd Class
Joined
Nov 3, 2012
Messages
81
Re: Attaching transducer to transom with epoxy?

Why not just install it inboard? I got tired of them getting damaged by water sports activities and fishing in timber. Moved inside ever sense and haven't looked back. Lots of how do do it on here.

Mark

Mark......I thought of that but I do want to have the temp reading. Thanks!
 

Yacht Dr.

Vice Admiral
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Feb 26, 2005
Messages
5,581
Re: Attaching transducer to transom with epoxy?

If done correctly, the epoxy should bond with the fiberglass skin of the transom and keep the water out. Most transom skins are at least 3/16 thick and that is penty of glass for the expoxy to bond to.

I agree that glueing a block to the transom and then scewing the unit to that is the most bulletproof option, but it may not be asthetically pleasing to some.

You are suggesting putting a large hole for a few #8 screws. Yes the screws will hold into the epoxy .. but the epoxy will not keep out the water. Drilling 1/2" epoxy filled screw bases will not keep out H2O .. it only makes the diameter larger for H2O to get in.

Yes .. bedding through hull fittings and screw holes below the waterline is a subject of some debate. I have given my advice. Drilling larger holes into fiberglass and replacing it with fiberglass/epoxy is redundant. Sealing any hole and mantantence is Key.

You dont need a sandwich of cutting boards or wood between your mounts .. you Need proper Bedding.

You can shoot down my other post if you like .. but Im sure I was spot on about How to Do This .. Both ways.

YD.
 

Augoose

Lieutenant Junior Grade
Joined
Mar 21, 2010
Messages
1,220
Re: Attaching transducer to transom with epoxy?

YD -So while you complain about someone else shooting down your post, you shoot down mine? :facepalm:

The only reason I used a "sandwich of cutting boards" is because the only available cutting board at my local walmart was only 1/4" thick - too thin for the 1" mounting screws for the transducer - hence the "sandwich". The point is I needed something thick enough to screw the transducer into. I should have explained that better in my initial post.

I agree that mounting the transducer plate directly to the transom with epoxy or 5200 COULD work, however not all transducer mounts, such as mine, have the appropriate surface area to get a good bond. Mine has a frame and is completely open in some spots, hence the need to be able to screw that into something solid which has an appropriate amount of surface area such as the poly cutting board. That poly will last way longer than wood and way longer than the boat or anything in it for that matter.

I suppose we can all agree that there are SEVERAL RELIABLE ways to do what the OP wants.
 

Yacht Dr.

Vice Admiral
Joined
Feb 26, 2005
Messages
5,581
Re: Attaching transducer to transom with epoxy?

YD -So while you complain about someone else shooting down your post, you shoot down mine? :facepalm:

No .. I suggested that anyone that would consider shooting down my post is welcome .. because I am Right on this.

Your welcome to disagree.

Yes it will - I used loctite marine epoxy and it worked great. My suggestion is this:
Pick up a cheap poly cutting board from walmart or somewhere else. Cut two, 2"x 2" squares (or whatever size square will marry up with the outline of your tranducer mount) and stack them together. Glue the two pieces together with the epoxy and then use the SS screws which came with the transducer mount to screw the mount into the poly board stack you made. Then roughen up the mating surface of the poly board along with the gel coat on the transom where you intend to mount the transducer. I then took a grinder and made a bunch of cuts in the mating surface of the poly board, about an 1" long by a 1/16" of an inch wide, to give the epoxy a better bonding surface vs a perfectly smooth surface with no depth.
Glue the whole thing onto the transom and give it several days to bond!
There are also commercial glue on mounts you can buy but they seem to be based on the same idea as above.
Good luck.

All Im saying is this is too much of an approach to bed the ducer down correctly.

I never gunned your post.. go ahead and gun mine down. You will not be able to. The OP can do what he wishes form the information given herein .. I give a step bye Step guide on How to do this. .. What do you give me ? .. Sarcasm and Bashing toward yourself. I give Information.. That is all I give.

What I have said in the post above yours is Correct .. you can state your reasoning behind that. Im not here to be little anyone. Not you or anyone else. .. but I can say for sure How to do this in Anyway.

Peace out.

YD.
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,670
Re: Attaching transducer to transom with epoxy?

Is the transducer ever going to need to be replaced? Time and history says yes.

Could the location need tweaking to get the best performance out of your electronics? yes.

Might you add a second transducer in the future? yes.

So it seems to me, that the best all around option is to either screw, thru-bolt, glue, or epoxy in a starboard mounting plate.
2.5x10 inches has worked well for me. Thru bolted on aluminum hulls, and epoxied on the glass hull.

Then screw the transducer to starboard.


The Stern Mate kit is also good, but lacks the adjustability for tweaking.
 

Augoose

Lieutenant Junior Grade
Joined
Mar 21, 2010
Messages
1,220
Re: Attaching transducer to transom with epoxy?

Wow.

YD, I'm not going to argue with you because it is clear that you are one of those types of people who is never wrong.

Hopefully someday you'll take that gigantic chip off your shoulder.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,588
Re: Attaching transducer to transom with epoxy?

Mark......I thought of that but I do want to have the temp reading. Thanks!

Well sir, I have come up against that argument more than once. I have a transducer mounted just off the keel and just in front of the transom. I do have an alum boat. On a glass boat it would depend upon how thick the glass was I'd imagine. Eventually it would come to the accurate temp. Question is how long would it take and just how much deviation you can stand.

I have another mounted to the underside of my trolling motor. Depending upon how fast the boat is moving, I have never had more than a 2 degree difference in the two instruments which dissolved to almost nothing after a few minutes.

Both are the same instrument model and type.

HTH,
Mark
 

barrynfla

Petty Officer 3rd Class
Joined
Nov 3, 2012
Messages
81
Re: Attaching transducer to transom with epoxy?

Well sir, I have come up against that argument more than once. I have a transducer mounted just off the keel and just in front of the transom. I do have an alum boat. On a glass boat it would depend upon how thick the glass was I'd imagine. Eventually it would come to the accurate temp. Question is how long would it take and just how much deviation you can stand.

I have another mounted to the underside of my trolling motor. Depending upon how fast the boat is moving, I have never had more than a 2 degree difference in the two instruments which dissolved to almost nothing after a few minutes.

Both are the same instrument model and type.

HTH,
Mark

I've been thinking about your idea of mounting it inside the hull. What did you use to mount your transducer and is the depth reading reasonably accurate? I'll be mostly in fairly shallow water so the fish finder isn't a big deal for me.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,588
Re: Attaching transducer to transom with epoxy?

I've been thinking about your idea of mounting it inside the hull. What did you use to mount your transducer and is the depth reading reasonably accurate? I'll be mostly in fairly shallow water so the fish finder isn't a big deal for me.

Transducers have a device inside that converts electrical signals to sound. Sound waves go through the water, strike whatever, are reflected back and the device receives the replies and converts them to electrical signals which are fed to your display. To transmit sound most efficiently, you need a hard surface.

So, in answering your new question, a hard setting epoxy with no bubbles is your best bet. They make and market epoxies that don't make bubbles when you mix the two ingredients. Or just take a regular 2 part epoxy and try to minimize the bubbles when you stir.....stir slowly. RTV would be a good thought, but RTV does not set up hard and any soft spots you have reduce your signal's efficiency.

You can answer the sensitivity question yourself. Park the boat in undisturbed water of the depth that approximates what you think would be most important to you. Put your transducer over the side, at the transom and take a reading.

Take a thin plastic bag, fill with water, insert the transducer and place it where you think you want to mount it. Compare readings.

While looking for the sweet spot, move it around to another location and tilt it looking for the best response.

Clean thoroughly and roughen up the selected mounting site. Build a little dam in the bottom of your boat out of something slick, like a plastic putty scraper and tape (so it's easily removed afterwards), mix and install your epoxy and your ducer ensuring that you coat the bottom of the ducer before placing where desired and that's it. If you have a tilt to it, just place something solid in the epoxy, as far to the side of the ducer as you can to hold it in place while the epoxy cures, or fixture up a temporary external support. When cured, remove your forms and you are good to go. Obviously the test bag is not involved in the installation. If your epoxy is not runny, you may not need the dam; just smear it on the boat and embed your ducer.

More questions ask.

Mark
 
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