Through Hull Transducer Adhesive

[CAR54]

3M 5200 has met it’s match, use debond spray formulated to remove 5200.

Using this product requires good ventilation and scorning the bead of 5200 with a razor blade knife on the thru hull depth sounder. Using a vibrating saw with a blunt blade on the exterior of the transducer I put the tip of the blade under the shoulder over lap of the transducer and worked the blade completely around the perimeter then sprayed.

It took two days of scoring and spraying once a day and on the third day the sealant became the consistency of jello. All the parts came apart easily after that.

Debond was bought on eBay.

[Compass790]

welcome to the forum
abg5088

I'm in the 4200 or lifeseal camp. 5200 too strong as you fear tho the debond sounds like a workaround. I dont think the thru hull requires that much strength but the seal is everything ESPECIALLY if you have a cored layup.

[wrwakefield]

My go to choice is Sikaflex 291 polyurethane since it can be used above and below the waterline for most applications.

It can also be tooled [and sanded] and painted when used above the waterline.

It is readily available even in remote locations.

Note you cannot tell the color of the product [black or white] by looking at the end [piston] cap; it isn't clear plastic.. You must instead read the ultra fine print on said end cap... Read the date too as shelf life is only 12 months unless stored in the freezer.

Also note it comes in two versions: LOT = long open time. I typically use the non-LOT as it provides plenty of open time for my uses.

As I recall Practical Sailor also gave Sikaflex 291 high marks in their testing regimens.

In case this is of interest.

Cheers! Bill

[kayakerChuck]

Welcome aboard!

I just did this- on my 1979 O'Day 30.

My transducer was leaking a little. I just pulled it out, cleaned the area of the old silicone, and used a bit of LifeCaulk when I re-installed.

[Cheechako]

I use 5200 on metal thru hulls and etc. But I would not use it on a plastic transducer.
While I am not fond of Silicone, and boaters diss it, it is amazing adhesive. Heck they hold large aquariums together with it. They hold skyscraper windows with Silicone blends too. I dislike having to remove the silicone , and be sure to scrape and remove it all.

[Rumrace]

Please give Lexel a look. Home Depot has it in 2 sizes but there are 3. It’s an adhesive with amazing memory. I’ve read about a lot of aging mounting goo from big brand failing and becoming out of solution. I’ve used their clear to mount stern drives over the goo Merc offers. Remounted side windows hatches sanction mounts.
It’s pretty good stuff

[George_SD]

I'm with someone else on the first - glass the hole and put in a in-hull transducer. Much safer and way easier to replace, don't need to haulout for it either.

If you want to go with a thruhull - i would still close the hole, make a new properly sized one for a kit that includes the based for a removable transducer (the one where you can take it out and then screw a cap to close it.