CONTINUOUSWAVE

I finally found the pictures from a couple of years ago I took during the fiberglass work on [the installation of a through-hull SONAR transducer on a 1984 Boston Whaler OUTRAGE 25]. I had posted about it earlier at
http://continuouswave.com/ubb/Forum6/HTML/003611.html

In short, I followed Airmar's instructions for a cored hull, but had to make a "stepped" hole since the hull thickness was too deep to engage the threads on the transducer. I drilled a large hole in the fish well on the port side, then a larger hole on the inside to seal off the core with resin and fiberglass, and then a larger hole yet to "countersink" the transducer nut slightly since the hull was too thick for the thread depth on the transducer.

I also bought some polyethylene rod that is the same diameter as the transducer - I got that centered in the hole and filled the space between the rod and the hole with the epoxy-fiberglass mix. I used fiberglass in the mix to better manage the heat. I could have used a straight epoxy if I had a special slow curing casting epoxy, but I used regular West epoxy and their standard slow hardener.

I wish I had realized I needed to male a stepped hole at first, as the way I did it, I had to cut out the epoxy "ring" and smooth off the top after I drilled the bigger hole. That was a pain to do in the tight space.

None of this is hard if you have basic fiberglass skills, and it is all hidden so it does not have to look pretty--just be clean and functional. I am convinced that worries about leaks into the hull core are overblown, and I doubt I will ever use a transom mount transducer again. This one reads accurately as shallow as one-foot under the keel, and I'm bumping then anyway.

Pictures are at
http://s1205.photobucket.com/user/russellbailey3/library/Transducer

I have wondered about drilling through the hull of my 22-foot Whaler at that same location, in the stern live well. There already is a hole there for the live well drain to the sea. I figured that would be the place to make a bigger hole and install the through-hull transducer.

I would like to see a photo of the installed transducer, both from the hull bottom and from the live well side. If you have those images, it would be great to see the finished work.

Looks like a pretty good solution. Too bad airmar didn't have more extended length transducer stems. As far as i can tell it's only the B744VL with fairing block. Are you planning on sealing the exposed core foam? I had considered taking this approach as well; but I am concerned about water accumulation in the counterbore for the nut.

brill - I did seal the countersunk area - I just did not get a picture of it after doing so and before I put the transducer in. I sealed the countersunk area just like I did the initial core, so it was 2x the work. When I sealed the countersunk area, I just packed the epoxy/fiberglass mix up between the hull skins and did not use a poly rod like in the initial hole - not quite as neat and took some sanding afterward - if I was to do it again I'd get a larger poly rod also as it makes it much easier to seal the hull. As an aside, it was a huge hole saw to make the countersunk area - maybe 7" or so - it was like spinning a plate with teeth. That transducer is an SS264w-200, which is their large size bore - putting in a B60 would not require nearly as big a hole but would still take countersinking for the nut.

jimh, I will get some "after" shots. I followed the recommendations on BOE Marine's website for installation of the transducer itself with tape and such - it worked very smoothly.
https://www.youtube.com/watch?v=QcBdkjCtifA
https://www.youtube.com/watch?v=nd-RPx34nUE

I did have a challenge getting the massive SS264 nut tight in the limited space I had to work - the special tool from Airmar would not work with the countersunk nut, and I could not get a normal wrench of any type in there either.. I ended up using a large wood clamp to get a good grip on the nut and tighten it down - something like this http://www.amazon.com/Bessey-HS-12-12-Inch-Handscrew-Clamp/dp/B0007D88XQ

Russ -

I recall some years ago, there was a thread regarding mounting a through-the-fiberglass-type transducer in a magazine. Evidently some models will allow for a "wet" installation where the transducer is mounted on the inside of a single thickness hull in a small cavity that's filled with oil.

The factory install point for through-the-hull transducers was up forward, and accessible under the small bilge area. As I mentioned in the earlier thread, we worked with the factory regarding the spot.

Regards - Don