Thread: Shoot thru hull transducer

Had leftover PVC and siliconed a 4" section around the factory cup. Will fill with water Monday and do a water trial this week if the lake level ever drops from all of this rain. I have the epoxy on standby in case I get a wild hair.

Prep the hull first by sanding out all of that silicone to begin with. You want to bond the transducer to naked fiberglass for the best results.

Be sure to test the transducer before you even start to think about mixing any epoxy. It won’t do any good to epoxy the transducer in place if it never worked there to begin with. Wish I had a dollar for every “professionally installed” transducer that was not tested prior to being epoxied in. Just use water to test it with and move the transducer around and test it until you get the strongest sonar returns on the display. Don’t forget to test it high speeds as well to make sure it will work than too.

If that is a Humminbird inside-the-hull transducer than it will come with its own epoxy. Most people think that more epoxy is better but it isn’t. All you need is a very think layer under the transducer to bond it to the hull. A thicker layer just absorbs the sonar signal when it is both transmitted and received. When you install it be sure to twist and squish all that unneeded epoxy out from under the transducer and than weight it down (a partially filled plastic bag of sand/dirt works good for this). Than leave it to fully cure and the temperature will affect this. For the Humminbird epoxy you need to allow 24 hours if the temperature stays above 77 degrees for the full 24 hours. At 60 degrees you need to allow 48 hours and do not use the epoxy at temps colder than this as it is a mess to clean out when it does not cure (I’m talking from experience here).

Be sure to clean the transducer with something that will remove oils and grease. I like to use denatured alcohol for this or at least some grease removing dishwashing liquid followed by several rinses in water. Scuff that transducer up slightly with some 400 grit sandpaper too so that the epoxy will get a better grip to (you will hate me for this when you try to remove it!).

Be sure to point the transducer in the right direction if it is a directional transducer like the Humminbird QuadraBeam transducer or the new DI transducer.


A water or mineral oil bath will work but I prefer to silicone down a piece of PVC pipe for this.

Thanks Greg! I have the siliconed sump filled with water and the Humminbird puck transducer inside (for a 718). There is a very small flat spot of fiberglass in my bilge to mount it to before the keep begins to rise so that is where I placed it. I haven't been able to test it on the lake yet but if the location is good, then I very well may epoxy it in when the temp stays above 60 during the night.

Greg, have you experienced or know of any decrease in signal on a transducer placed in a water or mineral oil bath as opposed to epoxied onto the fiberglass itself? Also, which do you prefer water or mineral oil? Thanks again.

Dutch552,
I haven’t noticed a difference between a well epoxied in transducer and one in a water/oil bath but than I have never compared the two side by side either.
I prefer water to the mineral oil because it is less messy to work with, easier to clean up if a spill occurs and is more available if you find that in the middle of the lake you need some!



You can also use this same method to install a transom mount transducer by mounting the hardware to the inside of the PVC pipe and not using the weight.

Originally Posted by cache22

If you have a water tight cup, just fill with mineral oil or water..... and set TD into it. Not really a need to epoxy!

My uncle used to do that.

What do you mean by a water tight cup?

Sealed to the hull with silicone sealant so it holds water.

Originally Posted by cache22

Sealed to the hull with silicone sealant so it holds water.

Thankyou, looks like a good idea. Since I'm not going to trust my HB 898 anymore I want to have another d f just in case.

Dennis