Thru-hull depth sounder transducer

A

Atomic_adam

New member
I've recently bought a new to me Lowrance LCX-15mt sounder/gps for my boat. I was hoping to mount the transducer on the inside of the boat and epoxy it to the hull. Lowrance has said it will work through 1/2" of fiberglass without any issues.
I was wondering if anyone new what the hull thickness on the smaller c-dory's is. I'm assuming there is no foam in the hull. I have a 14'.
 
You need to be sure that there is no core in the hull. If there is no core (foam, balsa, plywood), then you can mount the sounder transducer on the inside of the hull. Materials used are silicone, mineral oil, epoxy (no bubbles in any of these), or even water. I would put the transducer in a baggie of water and press this against the hull first to be sure it works.

There will be some attenuation of the signal--for example if you were getting 1000 feet, you will probably get 600 feet shooting thru the fiberglass. The sensitivity of the signal will remain the same (Image quality).

If there is any core, it will not work.
 
This thread has (unfortunately) become wholly relevant to me. Our venerable Navman plotter/fish finder (which we used solely as a depth meter/fish finder) gave up the ghost. I would dearly love to replace it with a unit that has an inside-the-hull transducer.

However ... the brochure for my vintage C-Dory says the two-inch-thick hull is balsa cored. If so, I'll probably need a stern-mount or through-hull transducer.

Has anyone successfully installed an internal transducer in a 2006 C-Dory 25?

Thanks!
 
Writer_Ron":21qq6nn7 said:
This thread has (unfortunately) become wholly relevant to me. Our venerable Navman plotter/fish finder (which we used solely as a depth meter/fish finder) gave up the ghost. I would dearly love to replace it with a unit that has an inside-the-hull transducer.

However ... the brochure for my vintage C-Dory says the two-inch-thick hull is balsa cored. If so, I'll probably need a stern-mount or through-hull transducer.

Has anyone successfully installed an internal transducer in a 2006 C-Dory 25?

Thanks!
Click to expand...
Ron, even with a balsa core in the cockpit and cabin floor, the hull itself is has many parts that are not cored. The bilge areas are generally not cored or are cored with a lesser amount of balsa and the areas under the berth are generally all glass (as are the sides of hull). In brief, I believe that almost all of the hull parts (not the cabin or cockpit floors) are not generally not cored (with the exception of the transom). Bob can speak more to the 25 but on the 22 I had and the Tomcat I now have, there were several places of solid glass where one could place and in hull transducer.
 
Ron,
I have to go by memory, but my recollection is that the 25 does not have the same type of sump, that the 22 has just in front of the transom, which is solid glass. The area forward of the helm bulkhead is not cored. But this is a bit far forward for a depth finder, since it may be out of the water, on in turbulence when the boat is at speed.

You can put a inside of the hull transducer in a cored bottom, by cutting out the inner layer of glass, then removing the core, and finally laminating glass from the inner layer to the outer layer all around this hole you have cut. This does two things. It seals the rest of the core from moisture intrusion. and it increases the thickness of the outer glass layer (by the amount you put on the inside--typical would be about 1/4" to 3/8" of biaxial cloth/mat, or mat and roving. There is no loss of stiffness of the hull doing this. Then you can use your conducting/coupling media of choice--including silicone, epoxy, mineral oil etc.

The thru hull is very do-able. You also have to remove the core. After cutting the hole the correct size for the transducer stem, you then route out the core material back 3/8 to 1/2 an inch, then fill this void with thickened epoxy. This does two things: seals the core and gives you an area for compression of the ring nut on the stem, without any danger of crushing the core. You can get flush to the bottom transducers, even with a cored boat--in that case, you may want to re-enforce the outer layer of glass slightly, since you have to chamfer the outer edge of the glass to match the angle of the transducer.

There may be reduced core--but no warrantee-- in the area where the bilge bilge pump is located just forward of the aft cabin bulkhead.
 
Bob - I'm not familiar with the 25's but don't they have a cockpit floor that is above the hull (in order to create a self bailing cockpit)? Is(Are) there not (a) bilge pump(s) down below near the aft end (like on a tomcat)? If so, I was assuming that bilge depression would be either un-cored or cored with a lesser amount of material.
 
The bilge depression under the cockpit floor on our 2005 25 was still cored but it was less than 1/2 inch of balsa in that circular space.

Greg
 
On my 22 the rear bilge pump sump still has a core, although it is thinner. I got 1 sounder to work there for a while, but I have a newer one that won't work. I think you need to be sure there is NO core.
Roger
 
Personally I have lost all faith in thru hull transducers. My Stingray came with a Faria depth gauge with thru hull. It was a $356. option that has never worked properly. No warranty because when you buy a new-non-current(2 year old) boat the warranty on any gauges installed by the builder (other than the Volvo rigging package) has already expired. Faria measures the warranty period from the time the gauge is sold to the builder!

After checking out the many various threads re. this problem on the My Stingray website I discovered that many people have had trouble with these. The marina that services my boat also tell me they have had to replace many of these gauges and sometimes decommission the thru hull and install a transom mounted transducer.

This is just my 2 cents

Regards, Rob
 
Aurelia":hlwtjhgv said:
The bilge depression under the cockpit floor on our 2005 25 was still cored but it was less than 1/2 inch of balsa in that circular space.

Greg
Click to expand...

That sounds somewhat familiar. That makes it relatively easy to remove the top layer of glass and the thinner core and back fill with epoxy/glass as Bob suggests. Of course the alternative is to mount it on the transom like most of us have. Using the standard over drill and fill method, there's no hole through the transom when you're done. If you mount a piece of starboard you can then mount the transducer to that and have the ability to adjust it without drilling new holes in the transom.
 
As roger suggests, the transom mount is easier (and sometimes cheaper) than the shoot thru the hull or thru hull mount. As Greg notes, there was a depression in the center of the cockpit under the hatch, where there is a bilge pump. The issue then becomes where do you put a bilge pump, if you put the thru hull there? --either under a step in the cabin, or all of the way back at the transom.

Yes there is a deck over the fuel tank--in the 2003 boat there was a step down area at the transom, with drains out the back--later boats had scuppers out the side if I am correct which would make it self bailing.
 
Aurelia":13p648c5 said:
The bilge depression under the cockpit floor on our 2005 25 was still cored but it was less than 1/2 inch of balsa in that circular space.

Greg
Click to expand...

That sounds similar to the sump at the center of the transom on my 22. It was very definitely cored (until I removed it), but the core was not as thick as the main hull core.
 
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