Transom Hole Filling

Hey folks, I've got a mid 80's Landau 1650 boat that looks to have had more than one motor on it with different mounting holes at some time. There are about four extra holes, about 3/8 to 1/2 inch, that I need to fill. I've been reading where some suggest using some stuff called Marine Tex (?), and I was wondering if that would be good for filling holes of this size? I had planned to fill the holes completely with it and then sand it smooth. Am I on the right track with this, or should I consider another method. Thanks for your help.

Here is the product you mention in your question: https://www.marinetex.com/marinetexepoxyputty.html
Maybe the FlexSet product they make would be better? https://www.marinetex.com/marinetexflexset.html
Here is what I used recently: https://www.pcepoxy.com/our-products/paste-epoxies/pc-11.php
I chose this product because the mixing ratio is 1:1,
I had previously used the marinetex product to seal some screw holes in my transom that I glued together, and did not like the 5:1 ratio of the mixing directions, it seemed like there was too much variability of how to accomplish that.
Mine will be all put back together in 4-6 weeks, and I can then report back as to how well thepc-11 worked on the holes I patched in the aluminum that had some holes similar to yours.
I'm sure someone else with more experience will chime in and steer you in the right way.
Take care.

pics would be helpful

Capt1972 said:

pics would be helpful

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I guess I could take some tomorrow. It's just a half inch hole that goes through the sheet metal and through the wood transom.

I closed up 13 holes in my transom ranging from 1/4" to 1/2". First I used a 5/8" counter sink bit on both sides of the hole then I cut some aluminum backing plates from .025 aluminum sheet.
I back buttered the backing plates with JB weld and masking tapped the backer to the inside of the transom. Then a little more JB weld to fill the hole from the outside of the hull covered in masking tape.
When the JB weld has cured sand it smooth.

doodlebug said:

Capt1972 said:

pics would be helpful

Click to expand...

I guess I could take some tomorrow. It's just a half inch hole that goes through the sheet metal and through the wood transom.

Click to expand...

I meant of the boat. We like boat pics!

I would not use JB weld, I would use an adhesive designed for prolonged underwater exposure unless we are talking about the marine version.. The Marine Tex would work fine

As far as mixing ratios, its not that critical to be precise, it will just change the hardening time if you are off a bit.

I see the marinetex comes in a white or gray mix. Which one would be best to use?

I have only used the white. not sure what the difference is, probably states in the product description if there is any difference

Ok, here are a few pictures as requested. She's isn't very pretty, all faded, carpet needs replacing transom needs all those holes filled, but it's solid. She could stand a good refreshing overall, but she floats. I'm in the process of parking a Johnson 70 hp on the back.

I think it looks great!!

I would carefully go over that transom, good chance the wood is rooted from all those holes in it!!!

You may have to change it out and possibly have those holes welded up

hard to say really

perchjerker said:

I think it looks great!!

I would carefully go over that transom, good chance the wood is rooted from all those holes in it!!!

You may have to change it out and possibly have those holes welded up

hard to say really

Click to expand...

A marine mechanic and I went over it pretty good. There was another motor mounted on there and those holes you see had a bolt through them and were sealed up nicely. The other holes were silicone real good. I plan to knock all that out and use that marinetex to seal them and then sand it down good and repaint the transom. We got a probe and checked the wood and it seems to be solid. Has a good solid sound when you tap it with a hammer. One more question, can you weld that even though there is wood right behind the metal?

oh I see

you will probably be ok then. From the pic it looks bad!

If you had it welded you would have to remove the wood

lckstckn2smknbrls said:

I closed up 13 holes in my transom ranging from 1/4" to 1/2". First I used a 5/8" counter sink bit on both sides of the hole then I cut some aluminum backing plates from .025 aluminum sheet.
I back buttered the backing plates with JB weld and masking tapped the backer to the inside of the transom. Then a little more JB weld to fill the hole from the outside of the hull covered in masking tape.
When the JB weld has cured sand it smooth.

Click to expand...

Is this basically what you're describing? Using the counter sink bit to give the JB weld "plug" something to grab onto?

I plan to use this method to patch a bunch of holes in my Gregor's transom, but I want Tomane sure I'm understanding you correctly...


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IMHO forget Marine-tex ... you want/need an epoxy that will flow and completely fill the voids. M-tex and/or JB Weld type of epoxies do NOT flow (nor penetrate the core!) and you can't be assured that you hit all the surfaces, although yeah ... you can at least verify that you simply capped off the hole with it ...

Look, for only $18 you can buy an epoxy sample kit from Raka epoxy, see: https://store.raka.com/epoxysamplekit.aspx . It includes 12-ounces of their standard marine epoxy resin 127, a sample of each fast 610 and slow 606 hardeners, a sample of silica and micro-bubbles fillers and lastly, a sample of standard 6-ounce fiberglass cloth. Raka epoxy is also a simple 2-to-1 mix ratio of resin to hardener, so you can mix as little or as much as you need.

Here's what I'd do. Cap one end of each hole with duct tape and put boat on a tilt with the 'open end' higher than the closed end. Fill with std thickness/thinness epoxy (see above). You will need a plastic syringe, but I have made do by pouring epoxy from a container and thru a plastic straw.

Use small cheap/disposable brush to ensure the epoxy penetrates the wood core. Fill to 'full' with mix using fast hardener, but note with any flowable epoxy, you won't be able to cap it full ... but hold on. Wait for this fill to 'kick', as in it starts to cure and gets tacky. Make some more mix (you only need a little!) and add the micro-balloons filler to the mix to thicken it akin to 'peanut butter' consistency, then swipe it into and over the hole. Clean up as well as you can. Micro-balloon sand easier than silica (also known as cabosil) but silica is the stronger of the 2 fillers. And one can always just use a little of each too. I have also used wood dust as a filler when laying up fillets.

Here's some pictures I took recently of plugging holes in a Boston Whaler transom. The pics don't show the entire process, i.e., the sanding, fairing and gelcoating, but when done ... you'd never know that any other holes were on that transom!

+1 on the epoxy repair. Just wanted to add the option to use finely cut fiberglass cloth (bunch it up & it shaves off nicely with scissors).

Mix that with resin for the filler & jam it in the hole. Have a pc of plastic sheet, some plywood, & a c clamp ready. The epoxy won't stick to the plastic sheet so cover the mash with that, then the ply & clamp shut until cured (usually overnight).

Good luck, nice boat BTW.

Maybe a new sheet of Aluminum or Diamond Plate to cover the repair area after you fill the holes too