Prepping transom holes for transducer mount

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Jersey Jim

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My new 2120SC arrives next week from the factory, and I want to have all my ducks in a row to get the side-scan transducer mounted to the transom. BOE marine who sells transducers, is recommending drilling over sized holes, filling them with epoxy, drilling pilot holes, THEN running self-tapping screws into the epoxy to secure the bracket. Looks like 3 or 4 holes on the ducer bracket, and they seem too close together to get that many over sized holes in a small area. All videos I find on prepping holes for this sort of thing, only show sealant on the screws & in the drilled hole. BOE says this is not good enough, and water will wick into the transom core in a couple of years. If there are any links/stickies on this topic, please direct me. Also, please give feedback on personal experience with water problems from sealant-only on screws.

I like the idea of a thick starboard plate, anchored down in the far corners, then just tapped holes in the plate for the transducer bracket. Then the 4 corner holes in the plate would be far enough away from each other to make them over sized. I've seen several uses of a mounting plate for this application.

Thanks
 

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Hi Jersey Jim!
I am an enthusiastic member of the over drill/thickened epoxy camp anytime I'm working with a cored workpiece. It's a bit more work (but not much) but why risk water intrusion. You have a good solid boat in the Parker. Keep it that way.
I like your idea of using a mounting plate of Starboard and affixing it to the hull and then screwing the transducer to it. Just be aware that almost nothing actually bonds to Starboard, not even 3m's 5200. So you are still going to have to use the over drill/thickened epoxy method. Also, I don't know if you can thread Starboard ...you might need a screw with more coarse threads. Test it on a scrap of Starboard before you commit your transducer.
 
The pix of that X-ducer takes only 2 screws.

12:00 & 6:00 or 3:00 & 9:00 which is what I'd use.
 
Personally, I would not mess w/ the starboard backing plate for mounting. It'll be a cleaner install directly screwed into transom. HOWEVER: you must use the overdrilling technique and backfill with thickened epoxy. Then, sand flush. THEN mount the 9 oclock and 3 oclock screws through your transducer bracket into the epoxy core (as Wart mentioned). Don't use all 4 mounting screws: overkill and unnecessary holes and epoxy in the transom. The elongated appearance of the mounting bracket holes will allow you to make microadjustments so you don't need to remove the mounting screws and relocate them after the fact... Update this thread once you've started so we can see pics! Congrats on the new Parker coming your way. You will LOVE your 2120. I LOVED mine. NEVER felt unsafe in that boat...

In this pic, you'll see that I drilled 3/8 inch holes through the glass, then back filled with thickened epoxy (RAKA w/ cabosil).



Then, I drilled 1/4 inch holes in the center of the epoxy plugs.



Then, I inserted the thru-bolts through the center 1/4 inch hole that was surrounded by epoxy. I used 4200 to seat the thru-bolts. SO, no where does the screw touch fiberglass, but epoxy only. See?:



This was the project I built: 19 foot Carolina Skiff DLX w/ dual stations for skinny water tarpon, redfish, trout and flounder fishing

 
warthog5":8szywb0i said:
The pix of that X-ducer takes only 2 screws.

12:00 & 6:00 or 3:00 & 9:00 which is what I'd use.
Click to expand...
The instructions show 3 mounting screws, 9:00, 3:00 & 6:00. The 6:00 screw is what gives it it's upward stability, as the water pressure wants to "lift" the transducer upward. However, the 6:00 slot does not have as much travel as the 9:00 &3:00, limiting the adjustment.

The 9:00 & 3:00 centers are 1.8" apart, and 1.4" from either of those to the 6:00 position. Plenty of space for 3 holes of 1/2" diameter or larger. Slots are .200" wide, so will accommodate 3/16" screws (#10) (0.1875"). Three #10 self-tappers were supplied.

Q #1: So how brittle is this epoxy? And will self-tappers bite into it without cracking or crumbling it?

The dealer won't install transducers, and I have my doubts they would go to lengths to protect the core with epoxy anyway. I will probably have to mount it at the dealer's lot, prior to them bottom painting it, or Q2: should I mount it afterwards? I just can't take it home and work on it there, as I am in the process of acquiring a larger tow vehicle.

Most importantly, ... Q #3: How do I retain the epoxy in a horizontally drilled 1/2" hole?

Lastly, Q #4: Where can I get it, & what is this epoxy called? I'm assuming its a 2 part mix.
 
This is the outline of the bracket. I traced 2 dimes to represent 3/4" holes to fill with epoxy, and the smaller was 5/8" diameter from tracing a washer. Clearly enough room between the 3 holes. So what size should I drill & fill? And what ready-to-use product?

 

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Jersey Jim":5bq2truz said:
warthog5":5bq2truz said:
The pix of that X-ducer takes only 2 screws.

12:00 & 6:00 or 3:00 & 9:00 which is what I'd use.
Click to expand...
The instructions show 3 mounting screws, 9:00, 3:00 & 6:00. The 6:00 screw is what gives it it's upward stability, as the water pressure wants to "lift" the transducer upward. However, the 6:00 slot does not have as much travel as the 9:00 &3:00, limiting the adjustment.

The 9:00 & 3:00 centers are 1.8" apart, and 1.4" from either of those to the 6:00 position. Plenty of space for 3 holes of 1/2" diameter or larger. Slots are .200" wide, so will accommodate 3/16" screws (#10) (0.1875"). Three #10 self-tappers were supplied.

Q #1: So how brittle is this epoxy? And will self-tappers bite into it without cracking or crumbling it?

The dealer won't install transducers, and I have my doubts they would go to lengths to protect the core with epoxy anyway. I will probably have to mount it at the dealer's lot, prior to them bottom painting it, or Q2: should I mount it afterwards? I just can't take it home and work on it there, as I am in the process of acquiring a larger tow vehicle.

Most importantly, ... Q #3: How do I retain the epoxy in a horizontally drilled 1/2" hole?

Lastly, Q #4: Where can I get it, & what is this epoxy called? I'm assuming its a 2 part mix.
Click to expand...

Personally, I would use the 12 and 3 position. You most likely will NOT need to make large adjustments, just minute ones once fitted. Don't use 5200 AT ALL, but a dab of 4200 fast cure OR life caulk would be appropriate on the facia side of your bracket ONCE YOU ARE DIALED IN ON YOUR SETTING.. in other words, don't put a sealent/ adhesive on there until you know that is you final X-ducer location (after you've sea trialed your application)... Then, use a bit of sealent/ adhesive.. I WOULD also use some on the number 10 screws Garmin provided.

I would drill a 3/8" hole and back fill (using a syringe to introduce the epoxy) into the hole. Once cured, sand flush to hull.

Brittle? No, not at all. Use a 1/16 inch bit to drill a pilot hole in the center of the epoxied' holes. Yes, the #10 screws will bite into the epoxy nicely w/ a small pilot hole.

I agree and would NOT trust a dealership to go through the extra steps to make it water tight. What do they care?

How to retain the epoxy in drilled holes on vertical surface? You thicken it with cabosil to a "mayonnaise to peanut butter" like consistency, then inject into the holes: just thick enough for it not to run. I would also use some painters tape to tape off the work area as to not "overdrip" the epoxy onto your nice new hull or bottom paint.

Where can you get it? I like RAKA out of Sarasota for my epoxy..but I buy it by the gallon...way overkill for this little project. I would hit your local west marine store and ask for their "west system" as I assume you can buy it in small volumes... you'll only use 10ml's or less... Also ask for their cabosil like product to "thicken" the epoxy. Cabosil NOT microballons: you are interested in strength of the product not sandable Fairness..

To apply before or after bottom paint? Either will work...but, if the dealership bottom paints, you'll have to get some 36 or 60 grit sand paper, sand off the desired area, and work with the gelcoated/ fiberglass transom. Don't install the bracket through the bottom paint. Ask the dealership to provide to you a courtesy 25 ml's of bottom paint in an air tight container for you to brush up the work area w/ bottom paint after your installation/ application is complete.

Can you visualize this??
 
Honestly... 3/4" holes can be used, but are a bit overkill.
I would go with something a bit smaller.
 
MarineTex is an epoxy that is the consistency of putty. That stuff gets hard as a rock...it can even be drilled and tapped.

Otherwise, use liquid epoxy and mix in Cabosil to the consistency suitable for your purpose.
 
Damn! You guys are good. I just drilled the holes to the depth I needed, shot 5200 in the holes then all over the screws and mounted it. Good thing mine never stays in the water more than a couple 3 days at at time. Not disputing any of this good advise. Just feeling inadquate. :shock:
 
Thanks for all of the great advice guys. Some of those project threads/links are amazing! In several posts, I've seen more of "plugging" unused holes more so than preparing the holes for use. Several of those examples use wooden dowels inserted in the midst of epoxy to fill most of the hole with wood. However, would just plain epoxy (no wood) in a 3/4" hole be good for running screws into? I guess my main question is, how large of a hole can epoxy be expected to cure without wood filler? And how many hours/days would be expected for say 3/4" diameter by 1-inch deep, to cure to the point of drilling/fastening? I don't want to hold up the bottom painters.
 
3/4" way too big... 3/8" is fine.
Use fast cure epoxy. It'll cure in 12 hours. No wood dowels... That's the point of the epoxy.... Water does not penetrate epoxy.
How large a hole can epoxy fill?... Larger than you intend to create with the epoxy plugs.

Right above your post is a "sticky" that Dale created called "small epoxy kit to keep on your boat". This is what you need to buy for your project…and source some "cabosil".

viewtopic.php?f=11&t=13420
 
sydngoose":cynwro59 said:
3/4" way too big... 3/8" is fine.
Use fast cure epoxy. It'll cure in 12 hours. No wood dowels... That's the point of the epoxy.... Water does not penetrate epoxy.
How large a hole can epoxy fill?... Larger than you intend to create with the epoxy plugs.

Right above your post is a "sticky" that Dale created called "small epoxy kit to keep on your boat". This is what you need to buy for your project…and source some "cabosil".

viewtopic.php?f=11&t=13420
Click to expand...

I followed Dale's link to the West G-Flex product. Watched many videos on all the West system products on their site. very informative. I just need to decide what sandable filler to add to it to get a non-runny consistency.


Is there any such thing as a stainless threaded insert that could be secured into the cored, bored & poured hole with that epoxy? Maybe a stainless "hex" insert of 10-32 or 10-24 size. Would be a shame to not be able to remove the mounting screws many times without damaging the epoxy threads formed by self tapping screws.

Can't wait to start tinkering again with all sorts of projects. A spear gun rack might be one of the first projects to install on the new "Madison Rose".
 
Pm me your address- I'll mail you an ounce of cabosil- that is all you will need w the g-flex system

You are overthinking this installation. No, don't add any hardware to the holes... You will not be removing the screws, just backing them out, adjust the mounting bracket, secure back in place... make micro adjustments. That is why the mounting bracket is slotted. Screws stay where you place them. The bracket moves... Then once you are happy w the final placement, a dab of 4200 behind the bracket to the hull. Secure the screws once last time...with a dab of 4200. Torque them down flush to the mounting bracket. Done.
 
Cabosil with a polyester resin makes a good filler. You can find both on Amazon. Check out this vid on mixing. You can put your mix in a syringe too.

Cabosil Filler Quart - Aerosil, Fumed Silica Powder, Thickener, Resins and More
Sold by: Pro Marine Supplies
$14.99

Polyester Laminating Resin-quart-includes 1 Oz Bottle of MEK Hardener
Sold by: Pro Marine Supplies
$24.99

http://youtu.be/jGPAx98pZmM
 
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