Epoxy for "over drill and fill" for exterior screws

[savery]

When mounting things (transducers, pitot tubes, etc) to transoms where there is wood behind the FG, best practice is to over drill the screw hole and then pilot drill/screw into the epoxy plug, thereby eliminating a path for water to get into the wood, right?

My question is - can a hardware store "marine" epoxy be used for this purpose (filling the over drilled hole), or do I need to buy $100 worth of epoxy/hardener/fillers to do this "right"?

Looking at something like this:
https://www.homedepot.com/p/Loctite-0-85-fl-oz-Marine-Epoxy-1919324/205361752

Trying to un-do some typical "half a tube of silicone oughta do it" work but don't want to make the situation worse.

Thanks!

 

[kcassells]

Yup that will work. So to make the job easier and faster you can predrill the holes then set your screws/dip with 5200.
For the penetration of the transducer I would over drill and fill with the pb like you said.
Add'l if the hole is overdrilled like you said then your screws may end up in the pb. I would still use 5200 on the screws.

 

[kcassells]

Yea just dinkin... The best way is to also have a glassed wood pad on the base of your hole to @1.5". Then drill that oversized hole and fill with pb. You do not want to screw into the hull at all.
Make the edges of the pad on 45 deg. angles so glass lays easy.

 

[dingbat]

If you really want to cheat the drill and fill ideology, mask off, then drill your hole just a hair over the outside diameter of the screw and a 1/4” deeper than the penetrating depth of your screws. Counter sink the hole(s) to prevent the gel coat from cracking

Now, spray your mounting screw(s) (Phillips heads) down with WD40 and sit it aside.

Now fill the drilled holes with marine-Tex Use a small tool (welding rod) to work the epoxy into the hole. Make sure their is no trapped air in the bottom and the hole is filled to the top.

Now take the screw(s) you set aside and screw then in the hole(s). Make sure you leave your ~1/4” buffer at the bottom of the hole. Let the screws dry in place for an hour or so and remove

At this point you have a sealed, “threaded” hole which to mount your “whatever”.

If you have a lot of apparatuses to mount, consider installing a transducer mount. Mine is 15” x 5” x 1/2”. Has two transducers, a speed sensor and a temp sensor. All mounted with just two holes in the transom.

Dont know what the fascination is with 5200.

5200 is not UV resistant. It dries out and cracks in as little as 3-4 years. If you must use anything, 4200 or 4000 UV is a much better product for sealing transducer mounts.

 

[kcassells]

If you really want to cheat the drill and fill ideology, mask off, then drill your hole just a hair over the outside diameter of the screw and a 1/4” deeper than the penetrating depth of your screws. Counter sink the hole(s) to prevent the gel coat from cracking

Now, spray your mounting screw(s) (Phillips heads) down with WD40 and sit it aside.

Now fill the drilled holes with marine-Tex Use a small tool (welding rod) to work the epoxy into the hole. Make sure their is no trapped air in the bottom and the hole is filled to the top.

Now take the screw(s) you set aside and screw then in the hole(s). Make sure you leave your ~1/4” buffer at the bottom of the hole. Let the screws dry in place for an hour or so and remove

At this point you have a sealed, “threaded” hole which to mount your “whatever”.

If you have a lot of apparatuses to mount, consider installing a transducer mount. Mine is 15” x 5” x 1/2”. Has two transducers, a speed sensor and a temp sensor. All mounted with just two holes in the transom.

Dont know what the fascination is with 5200.

5200 is not UV resistant. It dries out and cracks in as little as 3-4 years. If you must use anything, 4200 or 4000 UV is a much better product for sealing transducer mounts.

OMG...........HUH? tALK ABOUT WHAT WHAT.
While your at it buy a charcoal pizza oven.

 

[savery]

Thanks everyone, just wanted to make sure. Slapping "marine" on something doesn't really mean much except to the profit margin.

 

[mickyryan]

i predrilled all my outboard mounting holes oversized then redrilled through the epoxy i still think over drilling then filling and redrilling is the best way but maybe that's just me , i know a guy who has a boat all he ever does is drill fill with wd40 to let that act like a water proofing as the wood if able will soak up the wd40 basically making it waterproof and then he screws his screws in , i haven't tried this but his boat is 18 years old and never had a transom problem so maybe he got lucky , maybe he is onto something lol who knows

 

[poconojoe]

This is a moot point for you, but may help others with a clean virgin transom with no holes:

My transom had zero holes in it when I bought my used boat. I didn't want to make any holes so
I installed what was called a stern saver.

It's basically a block of Starboad that gets glued to the transom. Then you screw whatever you want to this block. No holes in your transom.
The kit comes with everything you need.

I suppose you could make your own stern saver, but for me, it was just easier to buy the kit.

It's now been on there solid for 9 years.