Thru-hull Transducer

Larry K · Posted: Wed Jun 07, 2006 6:09 pm Post subject: Thru-hull Transducer

Has anyone put a thru-hull transducer in a C-Dory 22ft cruiser or are you using the transom mount? How about the in-hall units and what one works best? I just bought a Raymarine C-80 with GPS and 18" Radome and am thinking of adding the digital sounder.

Any thoughts?

Larry K

Adeline · Posted: Wed Jun 07, 2006 6:44 pm Post subject:

Dora~Jean · Posted: Thu Jun 08, 2006 12:45 am Post subject:

I have a thru-hull with my Garmin 168 Sounder, love it, works at all speeds, no problems with sea-weed. You're right about the installation on the balsa core being a bit more complicated. But this was my second boat as such so was familiar with the process. You have to core out about 3/8" around the initial hole (use a bent nail in a drill) then fill with epoxy paste (epoxy mixed with microballoons), let set, install transducer with either Boat Life or 3M 5200. Probably another description of this procedure elsewhere on this site.

Tony · Posted: Thu Jun 08, 2006 8:46 am Post subject:

Dora jean .... the bent nail is genius........... I have a through hull siting on the shelf in the garage that I think I will try now with your in site. Thanks again. Tony

Larry K · Posted: Thu Jun 08, 2006 10:10 am Post subject:

Thanks for all the input. What location is best to mount the Thru-hull transducer. Could it be put in the well with the bilge pump or at the back by the drain plug were the hull is not as thick? Or the problems the same.

Larry K

Dora~Jean · Posted: Thu Jun 08, 2006 1:24 pm Post subject:

Well, since others are going to 'destroy' their boats cause of me -- better give a few more details on how I did it...
1) Research well exactly where you want the transducer. My CD-25 was easy, I placed it under the step just inside the cabin as you enter, right next to the water pump (had to relocate it slightly). Mine is about 3" from the keel to avoid turbulence. This step is about 1/3 from the transom towards the bow.

2) Drill a small 1/8" pilot hole from the inside out all the way through.

3) Drill your transducer diameter hole (mine was about 1 7/8") from the OUTSIDE towards inside, keeping the drill as perpendicular to the outside hull as possible because you want the transducer to sit perfectly flush.

4) Bend a 16 penny or larger nail 3/8 - 1/2" from end, chuck it in a drill and ream out the balsa core around the hole (easier from inside, keeps it out of your eyes!).

5) Before applying the 'pasty' epoxy mix, use some of the epoxy before mixing with microballoons to thoroughly wet the inside surface of the balsa core area, you want a good seal interface to the pasty epoxy mix.

6) Build up the epoxy slightly larger than the area, maybe 1/8" all around. Then after hardens, use your original drill (mine 1 7/8") to drill a clean hole through the epoxy over-build (remember outside towards in).

7) Liberally apply your choice of bedding compound and set into place, don't fully tighten until the compound sets up a little, then snug it up to seal well.

Mine is 3 1/2 yrs old, no problems whatsoever -- now where's that wood to knock on, hmmm. Hope this helps.

Papillon · Posted: Thu Jun 08, 2006 8:22 pm Post subject:

Dora~Jean,
I know you mean well, but based on your wording....

Sea Wolf · Posted: Thu Jun 08, 2006 8:33 pm Post subject:

whaler-

I think he means to go-a-drillin' with the boat on the trailer, maybe? Laughing

( I just read the rest of your post and see that you realized this too!)

But then, maybe this would be a test of how fast you can work under duress and how well the adhesives and fillers set up when submerged! Teeth

Me-?-- I'd try to see if I could use a shoot through transducer inside the hull without cutting the outside hull by removing only the inner fiberglass and balsa core and embeding the x-ducer. Might give up a small amount of definition, but rather do that than cut that outer hull up if possible. Smile

Joe.

rogerbum · Posted: Fri Jun 09, 2006 1:06 am Post subject:

You can do it in the water, you just have to turn the boat upside down. However, I'd recommend doing it while on the trailer.

Dora~Jean · Posted: Fri Jun 09, 2006 1:56 am Post subject:

At first I thought you guys were joking, why wouldn't ALL trailerable C-Dory's be on trailers!! Then I came to my senses, sorry 'bout that. Yep, gotta get the boat outta the water for sure before drilling holes.

I agree with you Joe, if I had it to do over again I'd cut down to the outer fiberglass layer (about 1/4" thick) and try the shoot-thru method first, if it doesn't work well you can always install all the way through later.

One down-side of mounting a thru-hull transducer is that if you ever want to replace or repair it, it's kind of a bear, or worse, you want a different manufacturer's unit or newer technology that is smaller in diameter. Then you'd have to make a filler cylinder or something.

Tony · Posted: Fri Jun 09, 2006 8:38 am Post subject:

Steve... Would you need to remove the old one when up grading. Sounds like with this install the transducer becomes part of the hull. Tony

lloyds · Posted: Fri Jun 09, 2006 10:47 am Post subject:

Most sailboats have permanently mounted sleeves for the transducer and the knotmeter. You bed the sleeve then pop the sending units in and out as necessary. Manufacturers tend to stick to a standard size for those types of units. The transducers are sealed with an O ring. I have pulled them out several times. Surprisingly, the water doesn't come in all that fast when you pull it out. There is a dummy unit attached to the thru hull to put in as you pull the transducer out. Kinda neat to pull one out and be able to look at the bottom of the body of water you are parked in.

Dora~Jean · Posted: Fri Jun 09, 2006 12:53 pm Post subject:

Lloyds, yes that's what I had on my tri, but for my paddlewheel (speedo). I liked it knowing you could pull out easily to do whatever. Got sand in it once on a trip to Morro Bay (long story), but we had a gusher when I pulled it to clear the sand. That 2" hole put several gallons in the special compartment in seconds before I could get the dummy plug back in. Didn't know they make the same thing for transducers -- must've been lurking in the 'powerboat' section when I ordered this one. Good idea.

You can get the old transducer out even if you seal it with 5200 (or lighter stuff preferable), might end up destroying the unit though, so would want to make sure THAT was the problem beforehand. Shocked

lloyds · Posted: Fri Jun 09, 2006 1:08 pm Post subject:

A couple gallons is a drop in the bucket, considering it is a 2" hole below the waterline. but I would prefer shooting through that last glass layer. I know it can work, and you don't have to worry about watertight integrity. I have seen some installations where they bed a small container around the transducer, which is resting on the glass, then fill it up with motor oil to take out the voids between the transducer and the glass. Have never heard anyone complaining about performance.

ffheap · Posted: Sat Jun 10, 2006 3:33 pm Post subject:

Hi Folks,

Anybody who has read anything that I have written, I will not drill any hole in my hull if I can help it. Sink drain goes into a bucket under the sink. I feel that anytime you drill through fiberglass into the core, no matter how much epoxy you use, you may create a problem, especially under the waterline. When I purchased my 1983 22' C-Dory, it had a transducer on the stern. I left it there, but have filled the screw holes with epoxy, and then used a caulking compound when the screw went in.

My theory, and you can listen or not, is just don't mess up you boat if you don't have to.

Fred