Westsail Owners Alliance - Thread: "In-hull Depth Finder"
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Thread: "In-hull Depth Finder"

12,268 posts on 2,444 threads   •   From Mar 07, 2004 - Jan 08, 2012


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In-hull Depth Finder

Brian Smith

anybody have experience with a norcross 'hawkeye' in-hull depth finder?? this old boat has enough 'holes' in her- for $110 this little baby will give you depth to 200', through 'solid fiberglass'... Hmm... where to mount transducer??

Brian Smith

OK, trying ot revive this thread here... Anybody sailing with a 'shoot through the hull' type depth finder/transducer system? Any recommendations, thoughts?

Jay Bietz


I installed the Navman 3100 kit that includes the masthead sensors and digital gauge, knot meter, depth sounder.

I tested out the transducer under the stb 1/4 berth after sanding off the paint to bare fiber glass. I tested the location by putting the sensor in a baggie of water then presssed the assembly against the hull. For install, I used regular Silcone to secure it to the hull after other adhesives interefered with the signal.

I have pretty good results -- a few times the depth goes crazy as the boat rocks or? something else happens. I don't know if this is normal behavior or special to Navman or my installation.

Things to avoid: Air pockets in the fiberglass and ashesive that block the signal or have air bubbles.

Others use a water filled tube inside the hull with the transducer inside.

Hope this helps.

Brian Smith

Hey Jay, thanks for the info- sounds like yours works well enough... Where did you buy?

George and Rayna Shaunfield

Brian, 2+ years ago I installed a Navman depth finder with a thru hull transducer in my Cape Dory 26. However, Navman's instructions said it could be installed as an in-hull puck. After testing with the transducer in a baggie of water and as a temporary installation, I used a tube of silicon sealant to form a large mound under a berth (hopefully without any air bubbles) and pressed the transducer into it so that it was approximately vertical. Well, that temporary installation is still working fine. I have not detected any problem with the signal, but so far have not been in water deeper than 300 feet even in the Gulf of Mexico.

I have bought a Navman fish finder for my W28 and plan to install the transducer as an in-hull puck also. I will install it under the V-berth, but have not yet decided what to use for installing it -- silicon, epoxy, etc.


Brian Smith

Thanks George- How thick is the glass layup at that point on a Cape Dory? One of my chief concerns with this type of transducer is its ability to shoot through our rather amply
thick fiberglass!

Where did you buy your Navman?

Jay Bietz

Navman is hard to find now -- not happy about that -- Navman did replace the display when a character failed.

I believe that Navman was purchased by North star... http://www.navman.com

I've seen the Navman VHF radios on Ebay from time to time.

I also recommend you look at devices the new NEMA 2000 networking protocol.

Good luck


I have had some amazing results with an in hull transducer installation. I bought one of the larger Lowrance plotter/sonars and used the inexpensive transom mounted transducer supplied with it. Lowrance want $300-500 for a thru hull unit and about $200 for an in hull puck only suitable for flat mounting.
I went down to the hardware store and played around with standard white drain pipe. I used a 4" end fitting along with a screw-on inspection cover. The type with the square on the top to get a wrench around. I made up a cardboard template to resemble the hull shape in the hanging locker then used this as a guide to cut the pipe angle on a chop saw. I then used a common epoxy putty to glue his to the hull. After mounting the tranducer to the modified inspection cover I filled the pipe fitting with mineral oil and screwed in the transducer. The assembly is very strong, looks not too bad and can be unscrewed for maintenance. I has been working at better than specifications for a year now. Total cost around $20. If you are concerned about the signal strength in different locations I would suggest you build dams from modeling clay large enough to hold sufficient water and then immerse the transducer temporarily. The whole idea is to keep air bubbles out of the water/oil.
Try It

Bud Taplin

The inside transducer works well if the hull is solid fiberglass. Do not try it if the hull is cored with some other material. Fortunately the Westsail hulls are solid fiberglass, and lots of it.

Brian Smith


J and Jenny


I've got no direct experience with the Hawkeye (the price does sound great) but if there are any other deals or if you prefer another model don't feel constrained to the in-hull puck models- any transducer can work inside the hull. I think Roger laid out the best path to follow, and just want to second it. Our Kendall came with an ancient Signet depth sounder and its standard ancient through hull transducer was/is mounted in a well inside the hull, also at the base of the hanging locker by the nav station. The well in our boat is not as simple or clean an installation as Roger's and had drained its oil by the time we purchased it, but since fixing and refilling the well it has worked great- we're very glad the previous owners didn't drill the hole. Good luck.


George and Rayna Shaunfield


Cape Dory's are well constructed boat, but the hull would certainly not be as thick at that of a Westsail. There are generally two methods for installing a transducer as an in-hull puck.

1. Epoxy directly to the hull so that transducer ends up level (no air bubbles, of course).
2. Epoxy a piece of PVC pipe to the hull with a street clean-out screw cap and submerse the transducer in mineral oil, or baby oil. The method that Roger used.

I have read reports of people having good results with both methods. The Navman manual actually suggests epoxying directly to the hull.

I shopped around for the best price at the time and believe I bought my Navman fish finder through go2marine.com.


Randell 'Randy' Kocurek

Question for the group:
If you want depths measured in thousands of feet, as well as 200 ft. and less, is it best/necessary to go with thru hull trnsducer? If so, does anybody have a recommendation as my boat is about to be hauled out.

Ivan and Jane

Airmar make most transducers, the P79 is a deep water in hull transducer, It was certainly used by Navman, and from what I have been told can be used by many others.We have one in ourW42 fitted mid-ship wired to Datamarine instrument.Hope this helps

Randell 'Randy' Kocurek

Thanks Ivan,
I'm still in the market for that transducer and depthfinder. And the boat is on the hard.

Mike and Ivana Meyran

For those of you who have used in hull transducers, did you use a certain angle (deadrise) or flat pucks? I ended up getting a flat one thru mailorder and wondering if I need to return it?

Bud Taplin

You do need to install the transducer with the face parallel with the waterline. You can achieve this by installing a fiberglass tube vertically inside the hull, with its ID just slightly larger than the diameter of the transducer. Then put some mineral oil in the tube, and push the transducer down into the oil. You cannot have any air between the transducer and the hull. Of course, you could also put a wad of epoxy putty on the face of the transducer and on the hull, then push the transducer onto the hull putty, and align it straight up and down. Tape in place until the epoxy putty hardens.

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