Depth Finder won't shoot through Hull

[Bones]

Looking for someone who may have encountered this problem on a 25.5 Hunter. Purchased a Hawkeye depth finder but can't get it to transmit through hull. Verified that it is working and followed all troubleshooting. My mounting area is approximately 1.5 ft. before the keel in the compartment below the forward berth just forward of the waste tank. I find it strange that there are three previous installations there. My question is "Is there a better place to mount it?"
Anyone else run into this problem?
Trying to avoid putting another hole in the boat, this is an interior install.

 

[Franklin]

how did you attach it to the hull? If you use caulking, then it is hard to get all the air out and may not work. Epoxy is better to use.

 

[Justin_NSA]

What Franklin said. It won't work thru air. I've heard people use epoxy, toilet bowl wax, mineral oil etc.

 

[Meriachee]

If you've verified it's working then it needs to be epoxied into place, according to the docs.

 

[ronhanson01]

My Airmar transducer mounted in the bilge requires the housing to be filled with a specific amount of RV antifreeze to eliminate the air gap between the transducer and the hull.

 

[kloudie1]

Interesting observations:
https://www.thehulltruth.com/boating-forum/15830-mounting-transducer-bilge-mineral-oil.html

 

[CrispyCringle]

When I installed mine (Hawkeye unit) I just used the procedure in the instructions. I used the water bag test to find a good spot in the hull, and then epoxied it to the hull. In both cases make sure the tranducer it pressed firmly to the hull.

 

[Bones]

Bones: After the failed water bag test I used the toilet wax like a friend of mine had successfully done on his boat. Did not work. Then I cleaned everything up, sanded the interior hull and glued it down with clear 4200. I have avoided epoxy to keep from having to chisel it back up, however, I am thinking clear epoxy now which is what seems to be the trick. What bothers me is it seems the water bag test should have worked.

 

[Bones]

OK, so "where" did you install it?

 

[CrispyCringle]

I have a 23.5 and installed mine in a rear location access point, so not much help there.

 

[rgranger]

I’m a previous boat, I got it to work with plumbers putty

 

[CrispyCringle]

I’m a previous boat, I got it to work with plumbers putty

Sounds like a confession.

 

[Crazy Dave Condon]

One big factor with whatever you do, the gel coat needs to be removed with the area sanded smooth and no air in between the the fiberglass hull and transducer. Then wipe down the area to remove any dust and debris. Another problem could be an air pocket in the hull itself that wii interfere too

As for application I never used epoxy as it woul make it difficult to remove particularly if there is ever an issue. The first thing to do is place the transducer into a large bag of water against the hull to see if it will shoot thru the hull. If not, move some more until it does

One thing I found that works well is plumbers putty making sure no air of course and building up on the side letting it sit overnight to allow it to harden. Works like a charm and @Kermit can attest to that fact

 

[Justin_NSA]

Sounds like a confession.

We are here to help!

 

[JohnShannon]

Are you trying to shoot through solid fiberglass? or is it foam core? Foam core is a problem many people say.

 

[Crazy Dave Condon]

Although dyvanecel is used in the hull, it is designed to shrink when layers of glas and resin are added for structural integrity. Not an issue as this method has been used in the past on other Hunter water ballast boats successfully

 

[JohnShannon]

No foam is fine as a construction technique, foam is bad if you want to shoot high frequency sound though it. Has a soundproofing effect which is opposite of what you want. If you thump around maybe you find some solid glass near the keel. Some have suggested that you can drill a hole through the hull top layer, scrape away the foam replace it with a resin soaked epoxy pad and then mount the transducer that is to say create a small area of solid glass in the otherwise foam core boat. My boat is foam core, I am stuck with the same problems, I would like a depth sounder some day.

 

[thinwater]

Although dyvanecel is used in the hull, it is designed to shrink when layers of glas and resin are added for structural integrity. Not an issue as this method has been used in the past on other Hunter water ballast boats successfully

I used to due UT for a living, including large fiberglass chemical tanks, not too different from boat hulls. You can really loose a lot of signal strength in fiberglass. If the two surfaces (inside and outside) are not precisely parallel and very smooth this causes a lot of beam dispersal. Add a foam core and perhaps a soft, muddy bottom, and the bottom reflection is simply not enough. Poor performance should be expected, not a surprise.

 

[Kermit]

Plumbers putty worked great for Dave and me. We tried the water bag test and never got any results. Once we smashed the transducer into the putty it worked great.

 

[CrispyCringle]

I dont really understand the aversion to epoxy. The Hawkeye transducer case is a type of plastic that will pop off of epoxy cleanly if you pry it off carefully. That is stated in the manual. As for a blob of epoxy in a bilge access that I never look at and looks pretty much like unfinished fiberglass anyway, who cares. Grind it off if it bothers you, that is if you were to ever move the location anyway. It clearly is a better sound transmitter that a wax or putty and the transducer stays put. But to each their own.